Multifunctional metal-organic frameworks constructed from meta-benzenedicarboxylate units.

Chem Soc Rev View Article Online

Published on 04 April 2014. Downloaded by University of California - San Diego on 14/09/2014 12:23:23.

REVIEW ARTICLE

Cite this: Chem. Soc. Rev., 2014, 43, 5618

View Journal | View Issue

Multifunctional metal–organic frameworks constructed from meta-benzenedicarboxylate units Yabing He,a Bin Li,b Michael O’Keeffec and Banglin Chen*b Metal–organic frameworks (MOFs), also known as porous coordination polymers (PCPs), are an emerging type of porous materials which are formed by the self-assembly of metallic centers and bridging organic linkers. Design and synthesis of organic linkers are very critical to target MOFs with desired

Received 22nd January 2014 DOI: 10.1039/c4cs00041b

structures and properties. In this review, we summarize and highlight the recent development of porous MOFs that are constructed from the multicarboxylate ligands containing m-benzenedicarboxylate moieties, and their promising applications in gas storage and separation, heterogeneous catalysis and

www.rsc.org/csr

luminescent sensing.

1. Introduction Metal–organic frameworks (MOFs), also known as porous coordination polymers (PCPs), are porous crystalline solids that consist of metal ions or metal-containing clusters (usually termed as secondary building units, SBUs) connected to multidentate organic ligands via metal coordination bonds. The idea a

College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua 321004, China b Department of Chemistry, University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas 78249-0698, USA. E-mail: [email protected]; Fax: +1-210-458-7428 c Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287, US

Yabing He

Yabing He earned his PhD in organic chemistry from Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, under the direction of Prof. Lianxun Gao in 2010. After that, he worked in the group of Prof. Banglin Chen at University of Texas at San Antonio as a postdoctoral Research Fellow. In 2012, he joined the faculty of Zhejiang Normal University. His current research focuses on the design and synthesis of porous materials and study of their gas adsorption and separation properties.

5618 | Chem. Soc. Rev., 2014, 43, 5618--5656

to make use of metal–ligand coordination bonds to construct porous materials, to a certain extent, was initiated by the discovery of a few coordination complexes, for example, Ni(4-Mepyridine)4(NCS)2, to take up gas/vapour molecules,1 and the establishment of single-crystal X-ray structures of a few coordination polymers.2 Given the fact that porous zeolite materials (Al3+/Si4+ as nodes, and O2/OH as linkers of the frameworks),3,4 Prussian Blue5–7 (Fe2+/Fe3+ as nodes, and CN as linkers), and other porous zeolite analogues such as porous metal phosphates8–10 and sulphides11 (metal ions as nodes, phosphate and sulphide as linkers in these frameworks) have been well established to exhibit gas/vapour sorption, it seems to be quite natural and rational to assemble organic linkers instead of inorganic components to form porous organic–inorganic hybrid solids. However, the concept to

Bin Li

Bin Li received his PhD in 2012 from Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, under the supervision of Prof. Zhong-Ning Chen. After obtaining his PhD degree, he joined the group of Prof. Banglin Chen at the University of Texas at San Antonio as a postdoctoral fellow. His current research interest focuses on multifunctional metal– organic frameworks.

This journal is © The Royal Society of Chemistry 2014

View Article Online


Review Article

Chem Soc Rev

construct such porous materials through the coordination polymer approach was not formally proposed until 1989–1990 by Robson et al.12–15 Initial extensive efforts to stabilize coordination polymers and thus to establish their permanent porosity basically failed. This is mainly because metal–organic coordination bonds are much weaker than covalent or ionic bonds in traditional porous materials, so structurally ‘‘porous’’ coordination polymers cannot withstand activation: once solvent guest molecules inside the ‘‘pores’’ of the structures were removed under thermal and/or vacuum activation, the frameworks were collapsed and could not rebound back to take up gas/vapour molecules. The breakthrough in porous coordination polymers was realized during 1997–1999 when a few porous coordination polymers were exclusively established experimentally for gas sorption isotherms by Kitagawa and Yaghi’s groups.16,17 The polymer explored by Yaghi et al., MOF-5 (later on also termed as IRMOF-1),17,18 particularly attracted wide attention because of its extremely high porosity with BET surface area over 3000 m2 g1. It was also during that period of time that the term ‘‘metal–organic framework’’ was formally coined by Yaghi et al. to highlight those stable porous coordination polymers,19,20 and to emphasize the similarity of these special types of coordination polymers with those traditional porous solid materials in terms of their framework structures, topologies and properties. Basically, porous coordination polymer and metal–organic framework are the same terms which are defined from two different perspectives: the term ‘‘porous coordination polymer’’ focuses on the bonding nature between metal ions and bridging organic linkers and structurally polymeric features from the chemistry point of view; while the term ‘‘metal–organic framework’’ highlights the similarity with traditional framework solids, particularly zeolite framework materials, and thus emphasizes the robustness and the porosity from the material point of view.21 The implementation of solvothermal synthesis, as exemplified in the construction of MOF-14,22 significantly facilitated

the development of porous MOF materials. Such a simple synthetic methodology enabled us to readily construct highly crystalline MOF materials to characterize their structures and thus to rationalize their framework topologies. Furthermore, MOF materials can be synthesized within a very short period of time (typically 24–48 h) to explore their functional properties. More extensive studies on the construction of porous MOFs and exploration of their framework topologies and porosities have revealed some underlying principles: (a) some very basic SBUs such as M2(COO)4 and Zn4O(COO)6 to stabilize the frameworks; (b) combination of these basic SBUs with organic linkers of specific geometries to form MOFs with predictable topologies; (c) the structure/topology dependence of porosities of the MOF materials. This significant progress has motivated Yaghi and O’Keeffe to establish the reticular chemistry for MOF materials,23–26 which has apparently helped them to target some extraordinarily highly porous MOFs such as MOF-177 and MOF-210 with a BET surface area over 6000 m2 g1.27,28 The richness of metal ions/clusters as the nodes and a large number of organic compounds as the linkers to construct porous MOFs have provided great promise to generate an enormous amount of new porous materials. In fact, a huge number of porous MOFs have been realized for their diverse applications in gas storage and separation, selective adsorption and separation of organic molecules, ion exchange, catalysis, sensing, and drug delivery over the past two decades.18,29–61 Among the diverse organic linkers, those containing carboxylate groups are of particular interest because of their preference to stabilize the MOFs through in situ formed SBUs such as M2(COO)4 and Zn4O(COO)6. If some very fundamental organic building subunits containing carboxylates can be realized, the incorporation of these organic building subunits with diverse aromatic backbones can lead to a number of organic linkers for the construction of porous MOFs whose structures, framework topologies, pore/cage sizes and thus porosities can be

Michael O’Keeffe was born in Bury St Edmunds, England, in 1934. He attended the University of Bristol (BSc in 1954, PhD in 1958, and DSc in 1976). He is Regents’ Professor of Chemistry at Arizona State University, where he has been since 1963. Past research has included investigations of conductivity, diffusion, defects, and non-stoichiometry in solids and experimental and theoretical studies of crystal chemistry. Over Michael O’Keeffe the last dozen years he has been applying the theory of periodic structures to the development of the theoretical basis of designed synthesis of materials, such as MOFs, consisting of linked molecular fragments of predetermined shapes (reticular chemistry).

Banglin Chen was born in Zhejiang, China. He received his BS (1985) and MS (1988) degree in Chemistry from Zhejiang University in China, and PhD from National University of Singapore in 2000. He has been working with Professors Omar M. Yaghi at University of Michigan, Stephen Lee at Cornell University and Andrew W. Maverick at Louisiana State University as a postdoctoral fellow during Banglin Chen 2000–2003 before joining the University of Texas-Pan American in 2003. He moved to the University of Texas at San Antonio in August 2009, and now he is a Professor of Chemistry.


Chem. Soc. Rev., 2014, 43, 5618--5656 | 5619

View Article Online


Chem Soc Rev

Review Article

Fig. 1 Illustration of the power of the basic m-benzenedicarboxylate organic building subunit to construct metal–organic polyhedra and MOFs such as MOP-1, tbo-type HKUST-1, nbo-based MOF-505 and rht-based PCN-61.

systematically tuned. Furthermore, by immobilizing different functional sites into the frameworks these porous MOFs will have wide applications. As shown in Fig. 1, the usage of the m-benzenedicarboxylate subunit for the construction of porous MOFs was initiated by the readiness of the subunit to assemble with paddlewheel Cu2(COO)4 SBUs to form a porous metal–organic polyhedron (MOP) by Yaghi62 and Zaworotko63 and a prototype porous MOF HKUST-1 (HKUST represents ‘‘Hong Kong University of ¨der Science and Technology’’) by Williams.64 Chen and Schro explored the first series of porous MOFs constructed from m-benzenedicarboxylate subunits and dicopper paddlewheel Cu2(COO)4 SBUs.65–67 These MOFs not only have the same topologies, but also have systematically tunable porosities for their gas storage. This work immediately attracted wide attention in the MOF community. Apparently, incorporation of these m-benzenedicarboxylate subunits with different aromatic backbones can not only generate a large number of tetracarboxylates but also a variety of hexacarboxylates and octacarboxylates for the construction of porous MOFs. In this review, we will summarize and highlight multifunctional porous MOFs constructed from these tetra-, hexa- and octacarboxylates consisting of the very basic m-benzenedicarboxylate subunits. Because these porous MOFs have very rich MOF chemistry in terms of their structures, framework topologies, porosities and pore functionalities, their applications in gas storage and separation, heterogeneous catalysis and luminescent sensing have been extensively explored, which have been outlined in this review.

5620 | Chem. Soc. Rev., 2014, 43, 5618--5656

2. Multifunctional MOFs based on di-isophthalates Scheme 1 summarizes the tetracarboxylic acids containing two m-benzenedicarboxylate moieties with different spacers between them, which have been incorporated into porous MOFs. The explored spacers include double bond, triple bond, polyphenyl, chiral binaphthyl, and nitrogen-containing heterocyclic rings. Most diisophthalate organic linkers can be easily prepared by the cross-coupling reactions such as Suzuki coupling, and the Sonogashira coupling reaction, as well as the copper-catalyzed azide–alkyne cycloaddition (CuAAC) reaction. 2.1

Gas adsorption

2.1.1 Copper di-isophthalate frameworks. A copper–tetracarboxylate framework MOF-505 was synthesized via a solvothermal reaction of 3,30 ,5,5 0 -biphenyltetracarboxylic acid (H4bptc, H4A1, see Scheme 1) and Cu(NO3)22.5H2O.65 The rectangular organic building blocks are connected by in situ formed squareplanar dicopper paddlewheel Cu2(COO)4 SBUs, giving rise to a three-dimensional (3D) structure based on the 4-coordinated nbo net. There exist two different types of polyhedral cages in the resulting framework, one of which is composed of 12 ligands connecting 6 paddlewheel SBUs, and the other one is formed from 6 ligands connecting 12 paddlewheel SBUs. The two cages are connected to each other by sharing three paddlewheel SBUs, and arranged in an alternating fashion in a 1 : 1 ratio, forming a 3D cage-stacking framework. Comparison of the H2 adsorption properties under different activation conditions revealed that


View Article Online

Chem Soc Rev


Review Article

Scheme 1

The representative di-isophthalate organic linkers used to construct MOFs.


Chem. Soc. Rev., 2014, 43, 5618--5656 | 5621

View Article Online


Chem Soc Rev

the created open copper sites have a favourable impact on the H2 sorption capacity of MOF-505. MOF-505 takes up 2.47 wt% of H2 at 77 K and 1 bar. After the pioneering work by Chen et al., the nbo-related MOF-505 analogues derived from linear di-isophthalate linkers and dicopper paddlewheel Cu2(COO)4 SBUs have gained tremendous attention because catenation is basically difficult in such cage-based MOF networks, and most importantly these types of MOF materials exhibit promising gas sorption properties because of their high surface areas, tunable pore sizes and open copper sites. Currently, further efforts have been devoted to increasing the surface area, optimizing the pore size and immobilizing specific binding sites within the MOF-505 series to maximize their gas storage capacities. ¨der et al.66,67 synthesized a series of copper–tetraSchro carboxylate frameworks (NOTT-100 to NOTT-109; NOTT represents ‘‘University of Nottingham’’), which were formed from a range of polyphenyl tetracarboxylates of varying length and functionalization (H4A1, H4A8-H4A12, H4A14, H4A16, H4A19) and dicopper paddlewheel Cu2(COO)4 SBUs, to investigate the role of pore size, linker functionalization, and open metal sites (OMSs) on H2 adsorption. These frameworks have the same nbo-based topology as that of the prototypal framework MOF505 except NOTT-109 (erroneously assigned the pts topology, see Section 5.2) due to the spatial obstacle of the bulky central aromatic groups in the ligand. The pore sizes can be tuned by the polyaromatic backbones. Due to the large pore volumes as well as the presence of open copper sites, all desolvated materials exhibit high total H2 adsorption in the range of 2.24–2.63 wt% under 1 bar and 4.02–6.51 wt% under 20 bar at 77 K, respectively. In the case of NOTT-107, introducing methyl groups to create smaller pores can increase the heat of H2 adsorption and thus uptake at low pressure; however, it also reduces the free volume and thus negatively affects the highpressure H2 adsorption capacity. Subsequently, the same group synthesized two more isostructural framework compounds,68 namely NOTT-110 and NOTT-111, via solvothermal reactions of Cu(NO3)22.5H2O and the corresponding ligands, (2,7-phenanthrenediyl)-diisophthalic acid (H4A20) or (2,7-(9,10-dihydrophenanthrenediyl))diisophthalic acid (H4A21), respectively, to investigate the effect of the curvature of the ligand on H2 adsorption. Compared with the tetraphenyl based analogue NOTT-102, the phenanthrene and 9,10-dihydrophenanthrene groups in NOTT-110 and NOTT-111 cover more cage surfaces than the biphenyl groups in NOTT-102, making the cages more compact in NOTT-110 and NOTT-111. Such structural features result in a significant enhancement of H2 adsorption in the low and medium pressure range (0–20 bar). At 77 K and 1 bar, the total H2 uptakes of the desolvated NOTT-110 and NOTT-111 reach 2.64 and 2.56 wt%, respectively. These values are 18% higher than that of NOTT-102, despite the similar BET surface areas and pore volumes for all desolvated frameworks. At 77 K and 20 bar, the total H2 uptakes for NOTT110 and NOTT-111 are 6.59 wt% and 6.48 wt%, respectively, which are approximately 8% higher than the capacity of NOTT102. Moreover, NOTT-110 shows a high total H2 storage capacity

5622 | Chem. Soc. Rev., 2014, 43, 5618--5656

Review Article

of 7.62 wt% at 77 K and 55 bar. This study indicates that the curved ligand incorporated into a MOF can improve H2 adsorption because it provides a pocket facilitating gas adsorption. Suh et al. used 1,1 0 -azobenzene-3,3 0 ,5,5 0 -tetracarboxylic acid (H4abtc, H4A3) to synthesize three MOFs (SNU-4, SNU-5 0 and SNU-5; SNU represents ‘‘Seoul National University’’) with the same nbo-based topology, and studied the effect of OMSs on H2 adsorption.69 Notably, the formation of OMSs can be controlled precisely by selecting different activation conditions. It was observed that in the presence of OMSs, the MOF has a higher H2 adsorption on both gravimetric and volumetric bases, probably due to a stronger interaction between OMSs with H2 molecules since the reduction of framework mass cannot completely explain the enhanced volumetric uptake. Combination of Cu(NO3)22.5H2O with 1,1 0 -azoxybenzene3,3 0 ,5,5 0 -tetracarboxylate acid (H4abtc, H4A3) or trans-stilbene3,3 0 ,5,5 0 -tetracarboxylic acid (H4sbtc, H4A2) under solvothermal conditions afforded two isostructural nbo-based MOFs (PCN-10 and PCN-11; PCN represents ‘‘Porous Coordination Network’’).70 The BET surface areas are 1407 m2 g1 for PCN-10 and 1931 m2 g1 for PCN-11, respectively. Compared to PCN-11, a significant reduction of surface area in PCN-10 is presumably due to the fact that a NQN double bond is thermally less stable than a CQC double bond. This result also suggests that MOFs containing CQC double bonds are more favourable than those with NQN double bonds in retaining permanent porosity after thermal activation. At 77 K and 1 atm, PCN-10 adsorbs 2.34 wt% of H2 while PCN-11 adsorbs 2.55 wt% of H2. At 77 K and 45 bar, the total H2 uptakes are 5.23 wt% for PCN-10 and 5.97 wt% for PCN-11. In addition, PCN-11 shows an impressive total CH4 uptake of 194 cm3 (STP) cm3 at 298 K and 35 bar. To incorporate a CRC triple bond into the original organic backbone in MOF-505, Hu et al. synthesized a MOF-505 analogue Cu2(ebtc) (ebtc = 1,1 0 -ethynebenzene-3,3 0 ,5,5 0 -tetracarboxylate, A5) by a solvothermal reaction of H4ebtc with Cu(NO3)23H2O.71 The activated MOF possesses a BET surface area of 1852 m2 g1, and takes up 2.58 wt% of H2 at 77 K and 1 bar, 178 cm3 g1 of CO2 and 31 cm3 g1 of CH4 at 273 K and 1 bar. Most significant is that the activated material shows extraordinarily high C2H2 uptakes of 252 and 160 cm3 g1 under 1 bar at 273 K and 295 K, respectively, which are systematically higher than those of 177 and 148 cm3 g1 found for MOF-505.72 Since both frameworks (Cu2(ebtc) and MOF-505) have similar OMSs and pore window sites, the arrangement of these open copper sites and their orientation with respect to each other are believed to play a crucial role in such differential interactions with C2H2 guest molecules. Concretely, the open copper sites deviate from linearity in MOF-505, while the open copper sites are oppositely aligned in Cu2(ebtc), which enforces their stronger interactions with the adsorbed C2H2 molecules. Another possible reason for the higher C2H2 uptake of Cu2(ebtc) might be attributed to the CRC bonds, which enhance their interactions with C2H2 molecules through weak p–p interactions. The same ligand was also used by other research groups to construct copper-based MOFs. For example, Sun et al.73 synthesized a pair of supramolecular isomers (PCN-16 and PCN-16 0 ) by controlling the


View Article Online


Review Article

assembly of dicopper paddlewheel Cu2(COO)4 SBUs and ebtc ligands. PCN-16 is virtually the same as Cu2(ebtc). Although the two isomers possess the same space group symmetry, their subtle differences in pore structures significantly impact their adsorption capacities. PCN-16 has a BET surface area of 2273 m2 g1 and a total pore volume of 1.06 cm3 g1, while PCN-16 0 possesses a lower BET surface area of 1760 m2 g1 and a lower pore volume of 0.84 cm3 g1. Accordingly, PCN-16 exhibits significantly higher H2 and CH4 adsorption capacities than PCN-16 0 . PCN-16 and PCN-16 0 adsorb 2.6 and 1.7 wt% of H2 at 77 K and 1 atm, and 191 and 111 cm3 (STP) cm3 of total CH4 at 300 K and 35 bar, respectively. An nbo-based MOF, PCN-46, was constructed by a solvothermal reaction of 5-ethynylisophthalic acid and Cu(OAc)2. Interestingly, the one-pot self-assembly process involves three-step sequential reactions: the oxidative coupling of 5-ethynylisophthalic acid followed by deprotonation of the di-isophthalic acid and the formation of MOF. PCN-46 exhibits impressive gas sorption capacities. It adsorbs 1.95 wt% of H2 at 77 K and 1 atm, rising to 7.39 wt% at 77 K and 97 bar. The isosteric enthalpy of H2 adsorption of 7.2 kJ mol1 at a low coverage is higher than those of other nbo-based MOFs such as NOTT-101 (5.3 kJ mol1), and NOTT-102 (5.4 kJ mol1), which might be attributed to the interaction between H2 molecules and exposed and delocalized p electrons in the polyyne unit in the ligand. In fact, a strong interaction between C2H2 and an nbo-based MOF Cu2(ebtc) containing alkyne units was also discovered.71 In addition, a comparison of PCN-46 with NOTT-101 and NOTT-102 indicates that replacement of phenyl rings by polyyne units leads to a boost of pore volume and H2 uptake. The CH4 and CO2 sorption properties were also investigated. The total CH4 uptake is 172 cm3 (STP) cm3 at 298 K and 35 bar. The total CO2 uptake is 22.5 mmol g1 at 298 K and 30 bar. Zhang et al.74 also made the same MOF, which was directly obtained by a solvothermal reaction of 1,10 -butadiynebenzene-3,30 ,5,50 -tetracarboxylate (bbtc, A6) and Cu(NO3)23H2O. Compared to PCN-46, the resulting MOF Cu2(bbtc) exhibits a significantly lower BET surface area (1014 and 2500 m2 g1 for Cu2(bbtc) and PCN-46, respectively) and H2 uptake (1.43 wt% and 1.95 wt% at 77 K and 1 bar for Cu2(bbtc) and PCN-46, respectively), which may be due to the different activation profiles and/or the quality of the samples. By utilizing a long tetracarboxylate with imide groups, N,N 0 -bis(3,5-dicarboxyphenyl)pyromellitic diimide (H4A24), Suh et al.75 synthesized two MOFs SNU-50 and SNU-51 by solvothermal reactions of the ligand with Cu(NO3)22.5H2O and Zn(NO3)26H2O, respectively. The two MOFs have entirely different structures. In SNU-50, the Cu2+ ions form dicopper paddlewheel Cu2(COO)4 clusters serving as square-planar SBUs that are linked with the rectangular organic building blocks to give rise to a 3D nbobased network, while in SNU-51, the rectangular tetracarboxylates are linked with the distorted tetrahedral Zn2(COO)4 SBUs to form a pts-based network. Interestingly, the Zn(II) ions in SNU-51 can be exchanged with Cu(II) ions with the retention of the pts-based net that is impossible to be produced through direct solvothermal synthesis. After desolvation, SNU-50 retained its structural integrity while SNU-51 collapsed. The desolvated SNU-50 exhibits a BET


Chem Soc Rev

surface area of 2300 m2 g1, and high adsorption capacities for H2, CO2, and CH4. It adsorbs 7.85 wt% of H2 at 77 K and 60 bar, 17.5 mmol g1 of CO2 at 298 K and 55 bar, and 155 cm3 (STP) cm3 of CH4 at 298 K and 60 bar. The high adsorption capacities of SNU50 might be attributed to its unique structural features combining the large pore volume, exposed copper sites, and imide functional groups. For comparison, NOTT-10367 constructed from Cu(II) ions and a long tetracarboxylate (A16) exhibits a lower total H2 uptake capacity of 7.22 wt% at 77 K and 60 bar despite a higher BET surface area of 2930 m2 g1, indicating that a MOF with imide groups might be much better for H2 uptake than a MOF containing simple benzene rings. Some experimental and computational studies show that bridging ligands with an aromatic-rich backbone can enhance the gas–framework interactions via the polarized p electrons. Thus, an aromatic-rich tetracarboxylate, (R)-6,6 0 -dichloro-2,2 0 diethoxy-1,1 0 -binaphthyl-4,4 0 -di(5-isophthalic acid) (H4A22) was designed and synthesized by our research group, and the corresponding nbo-based MOF UTSA-4076 (UTSA represents ‘‘University of Texas at San Antonio’’) was obtained by a solvothermal reaction of the ligand and Cu(NO3)22.5H2O in DMF/EtOH/H2O at 363 K under acidic conditions for 48 h. Due to the presence of the chiral binaphthyl groups in the organic linkers, UTSA-40 crystallizes in the chiral space group R32. After desolvation, UTSA-40a shows a moderately high surface area of 1630 m2 g1 and a pore volume of 0.65 cm3 g1. These values are comparable to those of MOF-505 but lower than those of NOTT-102. High-pressure gas sorption properties were studied in detail. CO2 and CH4 adsorption capacities are much higher than the corresponding value for H2, indicating UTSA-40a has the potential for use in H2 purification processes, which is comprehensively examined by IAST (Ideal Adsorbed Solution Theory) and breakthrough calculations. It was found that UTSA40a possesses higher working capacity and lower regeneration cost when operating at high pressure than the traditionally used zeolites NaX and LTA-5A. Furthermore, compared with the well examined MOFs MgMOF-7477 and Cu-TDPAT78 the regeneration cost of UTSA-40a is significantly lower despite its somewhat lower productivity. In general, significant enhancement of the surface area could be achieved by ligand extension. Following this strategy, Bai et al.79 constructed a new MOF-505 analogue, NJU-Bai12 (NJU-Bai represents ‘‘Nanjing University Bai’s group’’), with a high BET surface area of 3038 m2 g1, which was assembled from dicopper paddlewheel Cu2(COO)4 SBUs and a nanosized tetracarboxylate, 5,50 -(1,4-phenylene-2,1-ethynediyl)bis(1,3-benzene)dicarboxylic acid, (H4pdeb, H4A29). As expected, the ligand extension enlarges the sizes of the two polyhedral cages, their diameters reaching up to ca. 1.1 and 1.6 nm, respectively. Gas adsorption properties were investigated accordingly, and the results show that the evacuated sample NJU-Bai12 takes up 6.27 wt% of H2 at 77 K and 20 bar, which is among the highest of the MOF-505 series reported so far under the same conditions (the current highest one is 6.51 wt% in NOTT-103a).67 The initial isosteric heat of H2 adsorption of 6.8 kJ mol1 is comparable to that of PCN-46 (7.2 kJ mol1), but higher than those

Chem. Soc. Rev., 2014, 43, 5618--5656 | 5623

View Article Online


Chem Soc Rev

of NOTT-101 and NOTT-102 (6.3 and 5.3 kJ mol1 for NOTT-101 and NOTT-102, respectively), which is presumably due to the stronger interaction between H2 molecules and the delocalized p electrons in the alkyne units than that for the phenyl rings. In addition, NJU-Bai12 also exhibits an excellent CO2 uptake capacity of 19.85 mmol g1 at 298 K and 20 bar, as well as selective gas adsorption properties with a CO2/CH4 selectivity of 5.0 and CO2/N2 selectivity of 24.6 at 298 K. Later, a similar MOF compound HNUST-2 (HNUST represents ‘‘Hunan University of Science and Technology’’) was prepared in which the tetracarboxylate ligand was simply replaced by 5,5 0 -naphthalene-1,4diylbis(ethyne-2,1-diyl)diisophthalic acid (H4nded, H4A30).80 HNUST-2 exhibits a high BET surface area of 2366 m2 g1, and impressive adsorption capacities for CO2 (18.07 mmol g1 at 298 K and 20 bar), CH4 (85.6 cm3 (STP) cm3 at 298 K and 20 bar), and H2 (5.2 wt% at 77 K and 20 bar), which are systematically lower than those of NJU-Bai12. Using bis(3,5-dicarboxyphenyl)terephthalamide (H4A23) containing four carboxylate groups as coordination sites and two amide groups as functional sites, a MOF-505 analogue HNUST-1 was constructed by Zheng et al.81 After activation, HNUST-1 exhibits a moderate BET surface area of 1620 m2 g1 and pore volume of 0.571 cm3 g1, which are lower than those predicted from the single-crystal X-ray structure. The relatively lower surface area indicates that the framework undergoes partial collapse after activation. Despite this, HNUST-1 still exhibits a high CO2 uptake capacity of 93 cm3 g1 at 298 K and 1 bar, as well as good CO2/CH4 and CO2/N2 selectivities of 7.2 and 39.8 at 273 K, respectively. Furthermore, the adsorption enthalpies of CO2 and CH4 at zero coverage are calculated to be 31.2 and 23.4 kJ mol1, respectively. The higher CO2 adsorption enthalpy in HNUST-1 is attributed to the large quadrupolar moment of the CO2 molecule facilitating strong dipole–quadrupole interactions between the acylamide groups and CO2. This work highlights the fact that the strategy of inserting the bridging amide groups into MOF frameworks is a promising way to construct new porous materials for effective enhancement of CO2 capture capacity and selectivity. Along this strategy, a microporous nbo-based MOF HNUST-3 containing oxalamide units was synthesized by the self-assembly of dicopper paddlewheel Cu2(COO)4 SBUs and a tetracarboxylate ligand containing functional oxalamide groups, N,N 0 -bis(3,5dicarboxylatephenyl)oxalamide (H4A7).82 The presence of open copper sites and polar oxalamide groups in the framework leads to high adsorption selectivity of CO2 toward CH4 and N2. The Henry selectivites of CO2/CH4 and CO2/N2 reach up to 7.9 and 26.1 at 298 K, respectively. In addition, the high pressure gas sorption properties were examined. HNUST-3 can adsorb a total H2 of 6.1 wt% at 77 K and 20 bar, excess CO2 of 20.23 mmol g1 at 298 K and 20 bar, and excess CH4 of 135.8 cm3 (STP) cm3 at 298 K and 20 bar. The incorporation of accessible nitrogen donor sites into the pore walls of porous materials can drastically impact their gas uptake capacity and selectivity, especially for the CO2 capture due to the dipole–quadrupole interactions between the polarizable CO2 molecule and the accessible nitrogen site. Thus, the introduction of a nitrogen-rich 1,2,3-triazole ring into MOFs

5624 | Chem. Soc. Rev., 2014, 43, 5618--5656

Review Article

will be expected to improve the performance of CO2 adsorption. Based on this idea, a novel 1,2,3-triazole-containing tetratopic ligand, 5,5 0 -(1H-1,2,3-triazole-1,4-diyl)-diisophthalic acid (H4A41), was designed and synthesized via a copper-catalyzed click reaction. A solvothermal reaction of H4A41 with Zn(NO3)26H2O in DMF afforded NTU-101-Zn (NTU represents ‘‘Nanyang Technological University’’).83 In the structure, each tetrahedral Zn2(COO)4 SBU is linked with square-planar tetracarboxylate, generating a 3D pts-based network where the coordination-free triazole rings are exposed inside the channels. The activated NTU-101-Zn shows a very poor gas sorption capacity, which is expected due to the framework collapse upon activation. However, when the Zn(II) ions in the framework were post-synthetically exchanged with Cu(II) ions in a single-crystal to single-crystal (SCSC) fashion, the resulting NTU-101-Cu exhibited significantly improved gas adsorption properties. The activated NTU-101-Cu exhibits a BET surface area of 2017 m2 g1, and takes up H2 of 1.78 wt% at 77 K and 1 atm, CO2 of 101 cm3 g1 and CH4 of 20 cm3 g1 at 273 K and 1 atm. The high adsorption selectivity towards CO2 over CH4 is attributed to the open copper sites and the free nitrogen donor sites which are accessible within the porous frameworks for efficient interactions with CO2 molecules. To systematically study the effects of various functional groups on gas sorption properties of MOFs, four isostructural MOFs (PCN-305 to PCN-308) with various functionalized pore surfaces were synthesized from a series of V-shaped di-isophthalate ligands (H4A37–H4A40).84 Solvothermal reaction of 5,5 0 -(pyridine-3,5-diyl)diisophthalic acid (H4pdda, H4A37) and Cu(NO3)22.5H2O in DMA with a small amount of HBF4 afforded green crystals of PCN-305. Attempts to obtain the single crystals of other MOF compounds (PCN-306 to PCN-308) failed, but PXRD studies confirmed that they are isostructural with PCN305. In PCN-305, there are 1D irregular channels along the c axis, and the uncoordinated pyridyl functional groups point to the pore of the framework. Their gas sorption isotherms were examined. It was found that there is no apparent relationship between the gas sorption properties and different functional groups, and gas sorption is basically related to the textural properties in these isostructural MOFs. Of these compounds, PCN-306 without any functional group has the highest surface area and pore volume. PCN-305 with pyridyl functional groups has the highest selectivity of CO2 over N2, whereas PCN307 with methyl groups has the highest selectivity of CO2 over CH4. PCN-308 with CF3 functional groups exhibits a slightly higher H2 uptake of 2.67 wt% at 77 K and 1 atm. Note that the same MOF compound with pyridyl functional groups was also independently reported by Bai et al., and named as NJUBai10.85 The high-pressure gas sorption properties were explored in detail. The desolvated NJU-Bai10 exhibits the saturated excess volumetric H2 uptake of 48 g L1 at 77 K and 60 bar, which is the highest value ever reported among MOF materials in terms of the saturated excess volumetric uptake. The total H2 and CH4 uptake capacities reach 9.5 wt% (70.1 g L1) at 77 K and 100 bar, and 198.6 cm3 (STP) cm3 at 290 K and 35 bar, respectively. The saturated CO2 uptake is 20.5 mmol g1 at 298 K and 40 bar.


View Article Online


Review Article

Chem Soc Rev

Fig. 2 (a) The rhombicuboctahedral cage enclosed by 8 dicopper paddlewheel Cu2(COO)4 SBUs and 16 Cuddcpp ligands. (b) ‘‘ABAB’’ packing of rhombicuboctahedron layers in MMPF-1. Gas adsorption isotherms of MMPF-1 at (c) 77 K and (d) 195 K. Reprinted with permission from ref. 87. Copyright 2011, American Chemical Society.

There has been an escalating interest in constructing metalloporphyrin based MOF materials due to their potential applications for gas storage, sensors, and particularly heterogeneous catalysis.86 More recently, Ma et al. reported the synthesis of a porphyrin based MOF in which [5,15-bis(dicarboxyphenyl)porphyrin]copper(II) (Cuddcpp, Cu-A27) was linked by dicopper paddlewheel Cu2(COO)4 SBUs to form MMPF-1 (MMPF represents ‘‘Metal–MetalloPorphyrin Framework’’).87 In the assembly process, insertion of a Cu2+ ion into the center of the H2ddcpp unit (A27) occurred in situ. The structure of MMPF-1 consists of rhombicuboctahedra cages serving as supramolecular building blocks (SBBs) to sustain the 3D porous metalloporphyrin framework structure. In each cage, there are 8 open copper sites associated with the porphyrin rings of the ligands and 8 open copper sites from dicopper paddlewheel Cu2(COO)4 SBUs (Fig. 2a). The ABAB packing of the polyhedral cages in MMPF1 significantly constricts its pore size (Fig. 2b), which facilitates selective adsorption of H2 and O2 over N2, and CO2 over CH4. At 77 K and 1 atm, MMPF-1 takes up a large amount of H2 (50 cm3 g1) but a very limited amount of N2 (5 cm3 g1) (Fig. 2c). At 196 K and 1 atm, MMPF-1 takes up a large amount of CO2 (80 cm3 g1), which is much higher than the amount of CH4 (18 cm3 g1) (Fig. 2d). Typically, it is necessary to have rigid organic linkers and SBUs to construct stable porous frameworks, as discussed above; however, recent studies show that some semirigid and even flexible organic linkers can also be used to synthesize robust MOFs. For example, Zhou et al. reported two Cu2(COO)4-based MOFs (PCN-12 and PCN-120 ) using a semirigid ligand, 5,5 0 methylene-di-isophthalate (H4mdip, H4A32).88 Their structures are quite different from those of the MOFs assembled from linear di-isophthalates. In PCN-12, 12 dicopper paddlewheel units are linked with 24 isophthalates to form a cuboctahedral


Fig. 3 Different cage structures in PCN-12 and PCN-12 0 . (a) A cuboctahedral cage connects to six adjacent ones in PCN-12. (b) A trigonal prismatic cage connects to six adjacent ones in PCN-12 0 . (c) H2 adsorption isotherms for PCN-12 and PCN-12 0 at 77 K. Reprinted with permission from ref. 88. Copyright 2008, Wiley.

cage connecting to six others in three orthogonal directions to form a 3D net (Fig. 3a), while in PCN-12 0 , 6 dicopper paddlewheel units connect with 3 ligands to form a trigonal prism connecting to six others to form a 3D net (Fig. 3b). Notably, after desolvation, 12 open copper sites in cuboctahedral cages in PCN12 point toward the center of the cage, while all the open metal coordination sites in PCN-12 0 point away from the cavity of the polyhedron. Such different OMS alignment results in a remarkable difference in H2 uptakes for the two MOFs. PCN-12 exhibits the current second record-high H2 uptake of 3.05 wt% at 77 K and 1 atm, in contrast to an uptake of 2.4 wt% for PCN-12 0 under the same conditions (Fig. 3c). Liang et al.89 used a semirigid tetracarboxylate ligand, 5-(3,5dicarboxybenzyloxy)isophthalic acid (H4dbip, H4A4), to construct a robust copper-based compound with the same nbo based topology as MOF-505. After the removal of the guest and coordinated water molecules, the resulting material exhibits a high BET surface area of 1773 m2 g1 and exceptionally high CO2 adsorption of 173 cm3 g1 at 273 K and 0.95 bar, as well as good CO2/N2 selectivity at 273 K, which might be attributed to the structural features such as a cage-like framework and open copper sites. Presumably due to the semirigid nature of the ligand, combination of the same ligand with dicopper paddlewheel Cu2(COO)4 SBUs under different solvothermal conditions resulted in another compound with distinctly different architecture, which was reported by Goldberg et al.90 The dehydrated sample,

Chem. Soc. Rev., 2014, 43, 5618--5656 | 5625

View Article Online


Chem Soc Rev

however, exhibits a relatively low BET surface area of only 232 m2 g1. Subsequent to the publication reporting PCN-12, a series of MOFs (UHM-2, UHM-3, and UHM-4; UHM represents ‘‘University of Hamburg Materials’’), which are isoreticular to PCN-12, were synthesized to systematically investigate the influence of the incorporation of atoms with higher polarizability on the H2 uptakes.91,92 They comprise dicopper paddlewheel [Cu2(COO)4] units as connectors, and 5,5 0 -(propane-2,2-diyl)diisophthalate (dmcdip, H4A33), 5,50 -(dimethylsilanediyl)diisophthalate (dmsdip, H4A34) and 5,5 0 -(dimethylgermanediyl)diisophthalate (dmgdip, H4A35), respectively, as linkers. After the optimal thermal activation, the materials exhibit the specific surface area of 1692, 2430, and 1360 m2 g1, respectively. Furthermore, it was found that the H2 uptakes at 77 K and 1 bar as well as the isoreticular heat of adsorption values slightly increase in the order of X = C o Si o Ge. However, due to the incomplete solvent removal during the thermal treatment, it is difficult to derive a positive correlation between the polarizability of linker atoms and the H2 uptake. Indeed, DFT calculations reveal that the effect is relatively marginal with respect to the effect of geometric changes associated with the interchange of the central atom. When the linker dmsdip incorporated in the MOF UHM-3 was extended by two phenyl rings, the resulting ligand H4A44, when combined with dicopper paddlewheel units, afforded a topologically different network, called UHM-6, with two-fold interpenetration,93 which is isoreticular to that of PMOF-3 (PMOF represents ‘‘polyhedron based MOF’’) constructed from the ligand 1,3-bis(3,5-dicarboxylphenylethynyl)benzene (H4A45).94 In the single net, there are three different cages. The first cage corresponds to one cuboctahedron consisting of 24 bdc units of the ligands and 12 dicopper paddlewheel units. Each cuboctahedron is connected to the neighboring cuboctahedra by the linkers assuming the Cs conformation along the a- and b-axes, and the ones with C2 symmetry along the c axis. Such different types of linkage generated two other cages. One is surrounded by 8 paddlewheels and 4 linker molecules having C2 symmetry, and the other one is bordered by 2 paddlewheels that are connected by 4 linkers with Cs symmetry. The gas sorption was investigated accordingly. In comparison to PMOF-3, UHM-6 possesses a notably lower specific surface area (1200 vs. 1840 m2 g1) but has only a slightly lower H2 uptake (1.8 vs. 2.1 wt% at 77 K and 1 bar). In the following section, we will focus on some promising MOF materials for high-pressure CH4 storage, which are constructed from the dicopper paddlewheel Cu2(COO)4 SBUs and di-isophthalate ligands. A microporous material PCN-14 was synthesized by the selfassembly of 5,5 0 -(9,10-anthracediyl)diisophthalate (adip, A15) and dicopper paddlewheel [Cu2(COO)4] SBUs.95 The framework has two remarkable structural features: (1) every 12 adip ligands connect 6 dicopper paddlewheel SBUs to form a squashed cuboctahedral cage (Fig. 4a), bridging the anthracenyl rings in close proximity (2.6 Å between a H atom and the center of a phenyl ring from the adjacent anthracenyl group). Such an orientation of organic linkers within the framework system

5626 | Chem. Soc. Rev., 2014, 43, 5618--5656

Review Article

Fig. 4 (a) Squashed cuboctahedral cages in PCN-14, and (b) total highpressure CH4 sorption isotherms of PCN-14 at various temperatures. Reprinted with permission from ref. 96. Copyright 2013, American Chemical Society.

leads to the enhanced van der Waals potential pocket where CH4 can interact strongly with the frameworks; (2) the removal of coordinated water molecules from the terminal sites of the dicopper paddlewheel SBUs results in the formation of open copper sites that are approximately oriented toward the center of the cuboctahedral cages so as to maximize electrostatic interactions with guest species. The combination of a small pore diameter and available open copper sites permits a high absolute volumetric CH4 uptake of 230 cm3 (STP) cm3 at 290 K and 35 bar (Fig. 4b), which is higher than the widely referred DOE (Department of Energy) target of 180 cm3 (STP) cm3 for CH4 storage. The high CH4 adsorption capacity of PCN-14 was also confirmed by the recent studies (Fig. 4b).96,97 Snurr et al.98 employed a high-throughput computational screening method to identify a known MOF NOTT-107 with a high CH4 uptake, and predicted a potential storage capacity of 213 cm3 (STP) cm3 at 298 K and 35 bar. The reason for such a high CH4 uptake in NOTT-107 is believed to be similar to the one behind PCN-14. A series of MOFs (NOTT-100, NOTT-101, NOTT-102, NOTT-103, NOTT-109) have been chosen and examined as potential adsorbents for CH4 storage.99 They exhibit high CH4 adsorption capacities at 300 K and 35 bar (181–196 cm3 (STP) cm3) and excellent working capacities for CH4 at 300 K (104–140 cm3 (STP) cm3, from 35 to 5 bar). The gravimetric CH4 uptake in this MOF series systematically increases with increasing porosity, while their CH4 storage pore occupancy decreases with increasing pore size. Most significantly, an empirical equation was derived from the high-pressure CH4 adsorption isotherms capable of predicting reasonably well the CH4 storage performance of previously reported microporous MOF materials with a pore volume of less than 1.50 cm3 g1, thus providing a convenient method to screen MOFs for CH4 storage purposes. A new tetracarboxylic acid, 5,50 -(9H-fluorene-2,7-diyl)diisophthalic acid (H4fddi, H4A17), was developed by Duan et al.100 Reaction of this ligand with Cu(NO3)22.5H2O under solvothermal conditions afforded a microporous MOF named as ZJU-25 (ZJU represents ‘‘Zhejiang University’’), displaying a new topology derived from ssb instead of nbo. After activation, ZJU-25 exhibits a BET surface area of 2124 m2 g1, higher than that of MOF-505


View Article Online


Review Article

but lower than that of NOTT-102. More importantly, the open copper sites (1.21 nm3) and suitable pore spaces (5–9 Å) within ZJU-25a have enabled this MOF to take up a large amount of CH4. At 300 K and 35 bar, the absolute uptake of CH4 reaches the widely referred DOE target of 180 cm3 (STP) cm3. The CH4 storage can be further increased to 227 cm3 (STP) cm3 at 300 K and 63 bar. Shortly afterward, the same group reported another porous MOF ZJU-5 constructed using a new tetracarboxylate with Lewis basic pyridyl sites, 5,50 -(pyridine-2,5-diyl)diisophthalic acid (H4pddi, H4A13).101 Intriguingly, the interplay between moderately high volumetric BET surface area (1916 m2 cm3), open copper sites (1.54 nm3), and Lewis basic pyridyl sites (0.77 nm3) has enabled ZJU-5a to take up a large amount of C2H2 and CH4. At 273 K and 1 atm, the C2H2 storage capacity reaches 290 cm3 g1, which is the highest ever reported among any porous materials.34 At 298 K and 1 atm, the C2H2 uptake of 193 cm3 g1 is only slightly lower than 201 cm3 g1 and 197 cm3 g1 in two best MOFs (HKUST-1 and CoMOF-74) for C2H2 storage.72,102 The CH4 storage capacity reaches 190 cm3 (STP) cm3 at 300 K and 35 bar, which can be further increased to 224 cm3 (STP) cm3 at 300 K and 60 bar, about 85% of the new DOE target of 263 cm3 (STP) cm3 for material based CH4 storage if the packing loss is ignored.103 A carborane-based MOF NU-135 (NU represents ‘‘Northwestern University’’) with the same nbo based topology as that of the archetypal MOF-505 was constructed via a solvothermal reaction between Cu(NO3)22.5H2O and a boron-rich ligand (H4A26) consisting of a central quasi-spherical para-carborane unit and two terminal isophthalic acid groups.104 Compared to an isoreticular MOF NOTT-101 that contains a phenylene group in the middle of two isophthalic acid groups, which is approximately equal in length to a p-carborane, NU-135 has a slightly reduced pore volume (1.02 and 1.08 cm3 g1 for NU-135 and NOTT-101, respectively)

Scheme 2

Chem Soc Rev

but a greatly enhanced volumetric surface area (1900 and 1460 m2 cm3 for NU-135 and NOTT-101, respectively) as a consequence of the globular p-carborane subunit. Significantly, the interplay between the volumetric surface area and pore volume results in high volumetric adsorption in NU-135. The total volumetric CH4 storage capacity of NU-135 at 298 K reaches up to 187 cm3 (STP) cm3 and 230 cm3 (STP) cm3 at 35 bar and 65 bar, respectively. The CH4 working capacity from 65 to 5 bar at 298 K is 170 cm3 (STP) cm3. The total volumetric H2 storage capacity at 77 K and 55 bar is 49 g L1. The CO2 uptake at 298 K and 30 bar is 18.5 mmol g1. These properties are comparable to those of current record holders in the area of CH4 and H2 storage.32,33 2.1.2 Other metal di-isophthalate frameworks. Because of the strong binding of free Li+ sites with H2 molecules, loading Li+ ions into MOF structures is expected to be a promising approach to significantly enhance the H2–host interaction. ¨der et al.105–108 studied a series of anionic In(III)–tetraSchro carboxylate frameworks constructed from functionalized diisophthalate linkers of different lengths (Scheme 2). The organic cations within the as-synthesized materials can be exchanged with Li+ ions to afford the corresponding Li+-exchanged frameworks. Based on the coordination geometry at the indium centers and bridging ligands, these framework structures can be divided into the following two groups: (I) NOTT-204, NOTT205, NOTT-210, NOTT-211, NOTT-212 and NOTT-213; and (II) NOTT-200, NOTT-201, NOTT-206, NOTT-207, NOTT-208 and NOTT-209. The materials in the first group (I) crystallize in a tetragonal space group. Each In(III) center adopts an 8-coordinated geometry via binding to O-centers from four carboxylate groups to give a tetrahedral 4-connected metal node. Each ligand binds to four separate In(III) centers and acts as a square planar 4-connected node. Thus, these frameworks

Structures of the organic ligands H4L and resulting MOF materials.


Chem. Soc. Rev., 2014, 43, 5618--5656 | 5627

View Article Online


Chem Soc Rev

Fig. 5 (a) X-ray crystal structures of triporous units (labelled as A, B, and C) in NOTT-200 and NOTT-201 as representatives of the second group (II). (b–e) Comparison of N2 and H2 isotherms for the parent frameworks (NOTT-206, NOTT-200 and NOTT-208) and the Li+-exchanged frameworks (NOTT-207, NOTT-201 and NOTT-209) at 77 K. Reproduced from ref. 106.

have a non-interpenetrated pts-based structure. In the second group (II), the framework structures crystallize in a monoclinic space group and consist of two independent doubly interpenetrated networks. Each In(III) center in the parent framework is 7-coordinated via binding to O-centers from three bidentate chelating carboxylate groups and one monodentate carboxylate group, while in Li+-exchanged samples, In(III) centers are 8-coordinated by 8 oxygen atoms from four bidentate chelating carboxylate groups. Each ligand binds to 4 separate In(III) centers to yield an overall 4-connected diamond type structure for the anionic frameworks. As shown in Fig. 5a, these anionic frameworks are triporous. When going from the as-synthesized samples to Li+-exchanged samples, the cations in channel B are replaced by Li+ cations located within channel C. In the first group, replacing the organic cations Me2NH2+ in NOTT-204 by Li+ produces a more porous material NOTT-205 with higher H2 adsorption capacity. The increase in H2 capacity for NOTT-205 compared to NOTT204 mainly arises from an enlargement in pore volume rather than any increase in H2 adsorption enthalpy. The other members within the group (I), however, are not stable and lose porosity. In the second group, the N2 isotherms of the desolvated NOTT-206, NOTT200 and NOTT-208 show no adsorption, hysteretic desorption and

5628 | Chem. Soc. Rev., 2014, 43, 5618--5656

Review Article

fully reversible sorption, respectively (Fig. 5b). After Li+ exchange, the resulting desolvated NOTT-207, NOTT-201, and NOTT-209 show type-I isotherms with good reversibility (Fig. 5c). Similar kinetic trap effects were also observed in the H2 sorption isotherms at 77 K. The H2 desorption isotherms for NOTT-206 and NOTT-200 do not track the adsorption isotherms and therefore show marked hysteresis loops (Fig. 5d). Upon Li+-exchange, the H2 adsorption isotherms for the desolvated NOTT-207 and NOTT-201 show no hysteresis but enhanced H2 adsorption properties in terms of both capacities and adsorption enthalpies (Fig. 5e). In contrast, both desolvated NOTT208 and NOTT-209 having larger pores show reversible H2 sorption isotherms without hysteresis. An enhancement of 31% in the H2 storage capacity together with an increase of 38% in the isosteric heat of H2 adsorption is observed on going from NOTT-208 to NOTT-209. Considering that NOTT-208 and NOTT-209 have similar N2 uptake capacities and BET surface areas, the enhancement of H2 storage capacities mainly originates from a change in the charge distribution in the [In(O2CR)4] moiety by incorporation of Li+ ions, because inelastic neutron scattering (INS) experiments have confirmed that the adsorbed H2 molecules are predominantly interacting with the carboxylate groups rather than directly with the Li+ ions. Solvothermal reaction of Sc(OSO2CF3)3xH2O with H4bptc (H4A1) in a slightly acidified mixture of DMF–THF–H2O afforded the framework NOTT-400.109 Each Sc(III) center was bridged by carboxylate groups to form 1D chains, which are further linked to each other through tetracarboxylate anions to give rise to an overall 3D framework structure where 1D channels of an approximate size of 8.1 Å were formed along the b axis. Desolvated NOTT-400a shows a high BET surface area of 1350 m2 g1 among the Sc(III) coordination polymers, and as a consequence, achieves the highest H2 uptake for a Sc(III) based MOF material. The H2 uptake for NOTT-400a at 77 K and 1.0 bar is 2.14 wt%, rising to 3.84 wt% at 20 bar. The isosteric heat of H2 adsorption was estimated to be 5.96 kJ mol1 at zero coverage. Feng et al.110 constructed a porous Mg-based MOF, CPF-1 (CPF represents ‘‘crystalline porous materials’’), which was obtained by a solvothermal reaction of H4bptc (H4A1) and Mg(NO3)26H2O in a mixed solvent containing N-ethylformamide (NEF). The formation of CPF-1 is highly sensitive to the type of solvents being used. Only NEF/H2O can lead to the crystallization of CPF-1. CPF-1 consists of 41-helical rod SBUs linked by benzene units of the bptc to produce 1D cylindrical nanotubular channels with the diameter around 1.0 nm. The desolvated CPF-1 exhibits a moderate BET surface area of 853 m2 g1 and H2 uptake of 1.29 wt% at 77 K and 1 atm, and selectively adsorbs CO2 over N2. Lah and Zou et al.111 used bis(3,5-dicarboxyphenyl) terephthalamide (H4A23) to construct a 3D porous Co-based MOF [Co2A23(H2O)3]. The framework is composed of the dinuclear Co2(COO)4 SBUs linked by the organic ligands, forming a 3D network with a lon-derived topology where the SBU and the ligand serve as 4-connected tetrahedral nodes. It is well known that for regular tetrahedral nodes, there are two possible types of topologies, namely, diamond (dia) and lonsdaleite (lon) nets. Although the two structures are composed of fused 6-membered rings, all such rings in diamond have the chair conformation


View Article Online


Review Article

while those in the lonsdaleite assume both chair and boat conformations. In the case above, the preferential formation of both chair and boat conformations in fused 6-membered rings might benefit from the amide groups increasing the flexibility of the ligand. The desolvated sample exhibited a BET surface area of 106.6 m2 g1, which is significantly lower than the one calculated from the single-crystal structure, indicating that the framework underwent partial collapse or severe distortion during the activation. Moreover, the desolvated solid showed the hysteretic CO2 sorption behavior, which is ascribed to strong interactions of CO2 molecules with the host solid or the apparent structural changes upon uptake of CO2. Compared with the widely investigated homometallic microporous MOFs, the heterometallic microporous MOFs were relatively less reported. An unusual heterometallic microporous MOF Cu3Cr(sbtc)2 was synthesized by a solvothermal reaction of CrCl2, Cu(NO3)23H2O and trans-stilbene-3,30 ,5,5 0 -tetracarboxylic acid ligand (H4sbtc, H4A2).112 The structure of the compound is similar to that of PCN-11 except that there exist two kinds of paddlewheel SBUs, Cu2(COO)4 and CuCr(COO)4, in the framework. After desolvation, the compound exhibits a high H2 adsorption heat of 7.0–8.4 kJ mol1, leading to a significant H2 uptake of 2.7 wt% at 77 K and 1 bar, which reaches a saturation of 5.0 wt% at 28 bar. The total uptake is 6.0 wt% at 77 K and 60 bar. 2.2

Heterogenetic catalysis

A 3D porous In(III)-based anionic MOF was synthesized by a solvothermal reaction of the semirigid ligand, 5,5 0 -methylenediisophthalic acid (H4mdip, H4A32), with In(NO3)34.5H2O.113 The compound consists of the mononuclear [In(COO)4] nodes bridged by the tetracarboxylates to form a 3D 4-connected uninodal network where both the In3+ ion and the mdip ligand serve as 4-connected nodes. There exist two types of rhombic channels along the b axis where the disordered counterions Me2NH2+ ions reside. Because of the Lewis acidity of the In3+ ions, the catalytic activities were examined in the Lewis acidpromoted Friedel–Crafts alkylation of pyrrole with nitrostyrenes. Compared to the homogeneous catalyst In(NO3)321/2H2O, the reaction in water gave comparable conversion and higher yield, and the substrate scope is very broad in terms of nitrostyrenes. Furthermore, the compound can be easily recycled by simple filtration and reused three times without obvious loss of the catalytic activity. Aromatic azoliums are precursors to NHC (N-heterocyclic carbine), which are excellent ligands for transition metals and unique Lewis base catalysts. Thus, Hupp et al.114 incorporated an imidazolium tetracarboxylate (H4imta, H4A42) into a microporous MOF material via a solvothermal reaction of H4imta and Cu(NO3)22.5H2O. In the structure, each imta ligand is linked to four other imta ligands via the dicopper paddlewheel to form hexagonal channels into which the C2 carbon of the imidazolium is projected. The gas sorption properties are highly dependent on the activation temperature and time. Heating under vacuum at 473 K for 4 h produces the optimally activated sample, exhibiting a good CO2 uptake capacity of 1.8 mmol g1 and high IAST CO2/CH4 adsorption selectivity of 20 at 298 K


Chem Soc Rev

and 1 bar. The availability of OMSs and the charged azolium struts and counterions might be the main contributing factors for such high CO2/CH4 selectivity because these two elements create polar cavities that preferentially adsorb CO2 because of its quadrupole moment. However, the catalytic properties concerning NHC were not explored. It is well known that metalloporphyrins exhibit unique catalytic, electronic and optical properties. Thus, five porphyrinbased MOFs [Cu2(Mddcpp), M = Zn2+, Ni2+, Pd2+, Mn3+(NO3), Ru2+(CO)] were synthesized by the reaction of Cu(NO3)23H2O with the corresponding tetracarboxylic acid building block Mddcpp (M-A27). These porous complexes are isostructural, regardless of the identity of the central metal of the ddcpp moiety, adopting a structure similar to that of NOTT-109 and MMPF-1 due to steric congestion at the Mddcpp moiety.67,87 Their permanent porosities have been established using gas sorption isotherms. The use of THF as the activation solvent led to the optimal result among typical activation solvents. The surface areas were smaller than that of NOTT-109 because the guest DMF molecules in the cage could not be completely removed due to the smaller cage aperture compared to that of NOTT-109. In fact, weight loss corresponding to the loss of DMF molecules was still observed for a sample even after Soxhlet extraction with THF. Of the five complexes, [Cu2{Ru(CO)ddcpp}] has the largest BET surface area and H2 uptake despite the axially coordinated groups. Also, their catalytic performance was evaluated in cyclopropanation of alkenes. All five MOFs showed catalytic activity, but partial collapse of the frameworks occurred during the reaction. Nevertheless, this work highlights the fact that using metalloporphyrins as MOF building blocks is an effective method for incorporating accessible metal sites (AMSs) into MOFs. To expand the pore window and interior space, the same group also synthesized an elongated but geometrically equivalent ddcpp analogue, 5,15-bis(dicarboxybiphenyl)porphyrin (bdcbpp, A31), and used it to construct a new porphyrin-based MOF [Cu2(Znbdcbpp)].115 The 3D structure of [Cu2(Znbdcbpp)] is very similar to that of the above ddcppbased MOF [Cu2(Znddcpp)]. Compared with [Cu2(Znddcpp)], [Cu2(Znbdcbpp)] contains larger pore windows along the a and b axes due to the incorporation of the elongated organic linker and their different orientations. Although the microporous framework structure was unstable with respect to the removal of the guest molecules in the cavity, these larger pore windows might facilitate solution based heterogeneous catalysis. A metal metalloporphyrin polyhedral cage based MOF, MMPF-3, was prepared solvothermally from a custom-designed porphyrin ligand, 5,15-bi(3,5-dicarboxyphenyl)-10,20-bis(2,6dibromophenyl)porphyrin (dcdbp, A28) and Co(NO3)2.116 MMPF-3 is based on molecular building blocks (MBBs) Co2(m2-H2O)(H2O)4(COO)4 that afford the cubohemioctahedral SBBs serving as 12-connected nodes in the resulting fcu topology network. There exist three types of polyhedral cages: a cubohemioctahedron, a truncated tetrahedron and a truncated octahedron (Fig. 6a–c). The permanent porosity was confirmed by CO2 adsorption at 273 K with a surface area of about 750 m2 g1. Given the high density of cobalt metal centers (1.23 nm3),

Chem. Soc. Rev., 2014, 43, 5618--5656 | 5629

View Article Online


Chem Soc Rev

Fig. 6 Three types of polyhedral cages present in MMPF-3: (a) cubohemioctahedron, (b) truncated tetrahedron and (c) truncated octahedron. (d) Kinetic traces of trans-stilbene epoxidation catalyzed by heterogeneous MMPF-3, homogeneous Co(dcdbp), fcu-MOF-1, MMPF-2, PPF-1Co and in the absence of the catalyst. The molar ratio of trans-stilbene/TBHP/ catalyst was 1000 : 1500 : 1 for all of the catalytic assays. Reprinted with permission from ref. 116. Copyright 2012, Wiley.

its catalytic performance was evaluated in epoxidation of transstilbene using tert-butyl hydroperoxide (TBHP) as the oxidant in acetonitrile at 333 K. Control experiments show that in terms of both selectivity and overall conversion, MMPF-3 is more efficient than the homogeneous cobalt(II) metallated dcdbp and other cobalt based MOFs examined such as fcu-MOF-1,117 MMPF-2118 and PPF-1Co119 (Fig. 6d), which is attributed to the higher density of active cobalt centers and/or cooperative interactions between the active centers in MMPF-3. In addition, MMPF-3 can be reused for eight cycles without significant drop in its catalytic activity. Proline and its derivatives are well known asymmetric organocatalysts. Using L- and D-pyrrolidine-2-yl-imidazoles as chiral adducts, Duan et al.120 synthesized two enantiomorphs Ce-MDIP1 and Ce-MDIP2 having AMSs pointing towards 1D chiral channels. Solvothermal reaction of methylenediisophthalic acid (H4mdip, H4A32) and Ce(NO3)36H2O in the presence of L-N-tert-butoxylcarbonyl-2-imidazole-1-pyrrolidine (L-BCIP) in water gave the compound Ce-MDIP1. In the structure, the mdip ligands link the cerium ions through the carboxyl groups to

5630 | Chem. Soc. Rev., 2014, 43, 5618--5656

Review Article

form a non-interpenetrating 3D network containing 1D irregular chiral channels with a 10.5 6.0 Å2 cross-section along the a axis. The cerium ions have removable coordinated water molecules which are well positioned within the channels, and therefore have the potential to function as a Lewis acid catalyst. The asymmetric catalytic activities were assessed in cyanosilylation of carbonyl compounds. Ce-MDIP1 exhibited a high conversion and excellent enantioselectivity, and could be easily recovered by simple filtration and reused at least three times with a slight decrease in the reactivity and enantioselectivity. A homochiral porous MOF decorated with chiral dihydroxyl recognition sites was constructed from an enantiopure ligand, 3,3 0 -di-tert-butyl-5,5 0 -di(3,5-dicarboxyphenyl)-6,6 0 -dimethyl-1.1 0 biphenyl-2,2 0 -diol (H4A43), and Dy3+/Na+ ions.121 Heating a mixture of (S)-H4A43, DyCl36H2O and NaCl in DMF, HOAc and water at 373 K afforded single crystals of [DyNaL(H2O)4]6H2O [(S)-1]. In the structure, the adjacent Dy and Na atoms are connected by carboxylate groups to generate a left-handed helical chain with a helical pitch of 14.1273 Å running along the c-axis. Four adjacent helices are bridged by biphenyl backbones of the ligands to form a nanotube with an open size of B1.81 1.81 nm2. The two hydroxyl groups of the ligand are partly shielded from the open channels by the biphenyl rings, but are still accessible to guest molecules. Due to the presence of large chiral pores and available OH groups, the enantioselective separation capabilities were evaluated. (S)-1 exhibited remarkable selective inclusion of the L enantiomers over the D enantiomers for racemic mandelate derivatives (Table 1). The adsorbent can be recovered and reused without the deterioration of enantioselectivity for at least three cycles. Also, the photoelectrocyclization of tropolone ethers within (S)-1 was examined. After irradiation of the inclusion adducts at 365 nm for 10 min, the products were obtained in 490% yield with ee of 98.5% for tropolone methyl phenyl ether and 83.3% for tropolone ethyl phenyl ether, respectively. The high selectivity may originate from the porous structure coupled with an amphiphilic channel interior lined with chiral OH groups. The enantioselective ring-opening of meso-epoxides by aromatic amines was achieved using a homochiral MOF UTSA-32,122 which was obtained via a solvothermal reaction of (S)-6,6 0 -dichloro-2,20 diethoxyl-1,1 0 -binaphthyl-4,4 0 -bis(5-isophthalic acid) ((S)-H4A22), and Zn(NO3)26H2O. The dinuclear Zn2(COO)4 clusters are bridged by the organic linkers to form a 3D framework in which there Table 1

Enantioselective sorption of 1 toward chiral mandelate derivatives

Entry

R

Adsorbent

Substrate/adsorbent ratio

eea (%)

1 2 3 4 5

Me Et iPr Bn iPr

(S)-1 (S)-1 (S)-1 (S)-1 (R)-1

1:1 1:1 1:1 0.75 : 1 1:1

93.1 (L) 64.3 (L) 90.7 (L) 73.5 (L) 89.9 (D)

a

Letters in brackets specify the preferable isomer.


View Article Online


Review Article

exist 1D irregular pores about 3.2 10.0 Å2 along the a axis. The corresponding a-hydroxyamines were obtained in good to excellent yields with mediocre to excellent ee values. The reactivity and enantioselectivity originate from the Lewis acidity of open metal nodes formed after activation, which are immobilized in the homochiral framework. It is well known that the homogeneous hydrogen-bonddonating (HBD) catalyst is prone to undergo self-quenching, thus decreasing the catalyst solubility and reactivity. If the HBD catalyst is incorporated into the porous MOFs, such issues might be addressed. Roberts et al. reported the first such example of a MOF-based HBD catalyst,123 which is highly active for Friedel–Crafts reactions between pyrroles and nitroalkenes. Combining 1,3-di(3,5-dicarboxyphenyl)urea (H4A36), 4,40 -bipyridine, and Zn(NO3)26H2O under solvothermal conditions yielded a new microporous MOF named as NU-601 with non-aggregative N–H urea moieties projecting into the pores (Fig. 7a). However, the urea moieties are occupied by DMF solvent molecules via hydrogen bonding. To open the urea sites, it is necessary to remove the hydrogen bonded DMF, which can be easily achieved by solvent exchange with CH3NO2. No conversion was observed in the Friedel–Crafts reaction between N-methylpyrrole and

Chem Soc Rev

(E)-1-nitroprop-1-ene with 10 mol% of NU-601 in toluene; however, NU-601 shows high reaction activity in a mixed solvent of THF and CH3NO2. The results might be ascribed to the product inhibition in the non-polar solvent. More importantly, NU-601 is a more active catalyst for Friedel–Crafts reactions compared to the homogeneous catalyst 1,3-diphenylurea, and exhibits the reagent size selectivity (Fig. 7b). The catalyst can be reused five times with only a slight degradation of reactivity. 2.3

Luminescent sensing

Liang et al. synthesized a family of lanthanide MOFs with rutile topology using the ligand, 5,5 0 -(1H-1,2,3-triazole-1,4-diyl)-diisophthalic acid (H4A41).124 In these compounds, the dinuclear building blocks were linked by the ligand to form a 3D network where the triazole is uncoordinated. The Tb-based compound exhibits good selective luminescent sensing behavior to Cu2+ ions in aqueous solution. When the Tb-based compound was immersed in an aqueous solution of different metal salts, no significant change in luminescence intensity was observed for K+, while slight luminescence quenching was found for Co2+, Ni2+, Zn2+, In3+ and Cd2+ ions. Most notably, the luminescent intensity was selectively quenched by Cu2+ ions. The selectivity and sensitivity of luminescence quenching are probably induced by the highly selective coordination ability of the uncoordinated carboxylic acids and the triazole groups in the compound. A novel 3D calcium based MOF based on a naphthalene diimide chromophore has been synthesized via a solvothermal reaction of 5,5 0 -(1,3,6,8-tetraoxobenzo[lmn][3,8] phenanthroline2,7-diyl)bis-1,3-benzenedicarboxylate (H4A25) and Ca(NO3)24H2O.125 In the structure, the Ca2+ ions are bridged by carboxylate groups to form a 1D 41 helical chain with a helical pitch of 10.437 Å, which is further cross-linked to four adjacent chains through organic naphthalenediimide (NDI) moieties, leading to the formation of a 3D network. Due to the large voids of the framework, two such networks interpenetrate each other by strong intermolecular p–p stacking interaction between the p-deficient NDI rings. Interestingly, the compound undergoes a photochromic transformation from yellowish to dark green upon irradiation by sunlight, and can return to the original color in the dark. The photoinduced radical generation together with p–p electron transfer might be responsible for such photo-responsive behaviors.

3. Multifunctional MOFs based on tri-isophthalates Scheme 3 summarizes a variety of C3-symmetrical hexacarboxylate linkers containing three isophthalate moieties at the end, which have been incorporated into porous MOFs. 3.1 Fig. 7 (a) View of the structure along the a axis, and (b) catalytic activities of NU-601, diphenylurea, and a control. All of the reactions were performed for 36 h and monitored by GC using mesitylene as an internal standard. Reprinted with permission from ref. 123. Copyright 2012, American Chemical Society.


Copper tri-isophthalate frameworks

Lah et al. synthesized a C3-symmetric hexacarboxylic acid containing three isophthalate units, 1,3,5-tris(3,5-dicarboxyphenylethynyl)benzene (H6B3), and used it to construct two isostructural MOFs (PMOF-2(Zn) and PMOF-2(Cu)).126 Briefly, PMOF-2(Zn) was synthesized by a solvothermal reaction of Zn(NO3)26H2O

Chem. Soc. Rev., 2014, 43, 5618--5656 | 5631

View Article Online

Review Article


Chem Soc Rev

Scheme 3

The representative tri-isophthalate ligands used to construct porous MOFs.

with the ligand in DMF, while the copper analogue, PMOF-2(Cu) was obtained by a solvothermal reaction of Cu(NO3)23H2O and the ligand in the presence of a small amount of HCl. In the structures, the isophthalate units of the ligand are linked with in situ formed paddlewheel SBUs to form the cuboctahedral SBBs, which are covalently linked through the 5-positions of the isophthalate moieties by the 1,3,5-benzenetriyl-tris(ethynyl) part of the ligand to give rise to a (3,24)-coordinated rhtbased net, where the ligand and cuboctahedron are taken as 3- and 24-connected nodes, respectively (we see below that a more logical, and informative description of this topology is as a (3,4)-coordinated trinodal net ntt). Alternatively, the framework can be viewed as the face-centered cubic (fcc) packing of cuboctahedra in 3D space, which leads to two additional different kinds of polyhedral cages: one a truncated tetrahedron and the other a truncated octahedron. As shown in Fig. 8,

5632 | Chem. Soc. Rev., 2014, 43, 5618--5656

the cuboctahedron (cub-Oh) was composed of 24 isophthalates units from B3 ligands and 12 dicopper paddlewheel units. The truncated tetrahedral cage (T-Td) was formed by 4 B3 linkers and 12 dicopper paddlewheel units. The truncated octahedron (T-Oh) was composed of 8 B3 ligands and 24 dicopper paddlewheel units. One truncated tetrahedron is connected to 4 cuboctahedra, and one truncated octahedron is connected to 6 cuboctahedra, by sharing the triangular and square windows of a cuboctahedron, respectively, leading to a highly porous framework. Although these two MOFs are isostructural, their stabilities and sorption behaviors are distinctly different. When the samples were activated, PMOF-2(Cu) remained intact while PMOF-2(Zn) was not stable, losing its crystallinity. The activated PMOF-2(Cu) exhibits a BET surface area of 3700 m2 g1, significantly higher than that of the activated PMOF-2(Zn) (72 m2 g1). Also, the PMOF2(Cu) shows high H2 adsorption of 2.29 wt% at 77 K and 1 atm,


View Article Online


Review Article

Fig. 8 Three types of polyhedral cages in PMOF-2(Cu): cuboctahedron (cub-Oh), truncated tetrahedron (T-Td), and truncated octahedron (T-Oh).

reaching the maximum value of 5.0 wt% at around 30 bar. The total H2 uptake is 7.0 wt% at 77 K and 50 bar. Interestingly, the zinc ions in PMOF-2(Zn) can be entirely replaced by Cu(II) ions via postsynthetic transmetalation. The complete transmetalation led to full recovery of the sorption capacities.127 Clearly, this study indicates that construction of metal–organic polyhedron based MOFs is a very effective route to obtain the MOFs with high surface area and large H2 storage capacities. With this strategy, solvothermal treatment of an elongated hexacarboxylate ligand, 1,3,5-tris(3 0 ,5 0 -dicarboxy[1,1 0 -biphenyl]4-yl)benzene (H6B12), with Cu(NO3)23H2O yielded a rht-based MOF NOTT-112.128 Similar to PMOF-2, the overall structure of NOTT-112 can be viewed as the packing of three types of polyhedral cages, namely, cub-Oh, T-Td and T-Oh, in the ratio of 1 : 2 : 1 in 3D space (Fig. 9a). The hierarchical porous structural feature is also reflected in the N2 adsorption isotherm collected at 77 K showing small changes of slope in the relatively low

Chem Soc Rev

pressure region, indicating that the different sized cavities are filled in sequence as the pressure increases. The fully evacuated framework NOTT-112a exhibits a high BET surface area of 3800 m2 g1 as well as excellent low-pressure and high-pressure H2 adsorption capacities (Fig. 9b): total H2 uptake of 2.3 wt% under 1 bar, and 10.0 wt% under 77 bar at 77 K. This efficiency in adsorbing H2 at low pressures can be attributed to the presence of exposed copper sites within the relatively small cuboctahedral cage, which has been experimentally confirmed by neutron powder diffraction (NPD) studies of D2 adsorption in desolvated NOTT-112a revealing that the exposed copper sites within the smallest cuboctahedral cages are the primary binding sites for D2 in this material.129 The D2–Cu distance of 2.23 Å is shorter than the D2–Cu distance of 2.39 Å observed in HKUST-1,130 clearly indicating that a specific geometrical arrangement of exposed Cu(II) sites can strengthen the interactions between D2 molecules and OMSs. In fact, a similar cage has also been found in PCN-12,88 which exhibits an exceptionally high H2 uptake of 3.05 wt% at 77 K and 1 bar. The efficient high-pressure performance was attributed to its high surface area and pore volume. Thus, this study suggests that mixing of small and large polyhedral cages with open copper sites represents a powerful strategy to optimize H2 uptake over extended pressure ranges. Later, the same group synthesized two expanded MOFs NOTT-116 and NOTT-119,129,131 which are isoreticular with the above-mentioned NOTT-112. As expected, increasing the size of the central part of the ligand enlarges the sizes of the T-Oh and T-Td, but does not change the size of the cub-Oh. NOTT-116 incorporating an elongated nanosized ligand H6B6 within the framework shows a higher BET surface area of 4664 m2 g1 relative to NOTT-112, and a total H2 adsorption capacity of 9.2 wt% at 77 K and 50 bar.129 NOTT-119 was based on a more extended nanosized hexacarboxylate linker H6B14.131 Intriguingly, the N2 isotherm for the activated NOTT-119a shows typical Type-IV behavior with a slight adsorption–desorption hysteresis, which might be due to the unique hierarchical polyhedral structure. The flexible nature of the framework is another possible explanation proposed by Zhou et al.132 Compared to NOTT-116a, NOTT-119a has a higher pore volume but lower surface area (4118 m2 g1). NOTT-119a shows a high total H2 uptake of 9.2 wt% at 77 K and 60 bar, and total CH4 uptake of 165 cm3 (STP) cm3 at 298 K and 80 bar. From the H2 adsorption data summarized in Table 2, it can be seen that when the pore volume increases from NOTT-112a to NOTT-119a, the maximum excess adsorption

Table 2 Comparison of textural properties and H2 adsorption in NOTT112, NOTT-116 and NOTT-119

MOFs

Fig. 9 (a) Different cages in the crystal structure of NOTT-112, and (b) high pressure H2 adsorption isotherms for NOTT-112 at 77 K (red: total uptake; blue: excess uptake). Inset: total H2 uptake at 78 K and 88 K up to 1 bar. Reproduced from ref. 128.


BET (m2 g1) Vp (cm3 g1) Pmax a (bar) Csat b (mg g1) Ref.

NOTT-112 3800 NOTT-116 4664 NOTT-119 4118

1.62 2.17 2.35

35 27 44

76 68 59

128 129 131

a Pmax indicates the pressure where the maximum excess H2 adsorption at 77 K was reached. b Csat corresponds to the saturated excess H2 adsorption capacity at 77 K.

Chem. Soc. Rev., 2014, 43, 5618--5656 | 5633

View Article Online


Chem Soc Rev

pressure first decreases and then increases, while the saturated excess H2 adsorption capacity decreases, indicating that simply increasing the available pore volume cannot secure an increase in gas uptake, and therefore there exists an optimum pore size and geometry for H2 storage. When the size of the linker is further extended beyond the one in NOTT-119, the network is no longer stable against the conventional thermal activation. For instance, the isostructural rht-based MOF NU-100,133 also known as PCN-610,134 which incorporates a slightly longer ligand (H6B8) than that in NOTT-119, undergoes complete loss of porosity upon thermal desolvation under vacuum. However, this mesoporous network retains crystallinity on activation using the mild supercritical CO2 drying (SCD) method. The resulting NU-100 exhibits an ultrahigh surface area of 6143 m2 g1 and the excellent gas sorption capacities for H2 and CO2. The maximum excess H2 adsorption capacity is 9.95 wt% at 77 K and 56 bar, which is the highest one reported thus far.32 The total CO2 storage capacity for NU-100 at 298 K and 40 bar is 52.61 mmol g1, one of the largest values yet reported for MOF materials. To investigate the effects of pore surface decoration on gas adsorption, the same group synthesized a series of isoreticular frameworks based on the (3,24)-coordinated rht net: NOTT-113, NOTT-114 and NOTT-115, which are constructed from dicopper paddlewheel SBUs and the hexacarboxylate linkers H6B4, H6B5 and H6B13, respectively.135 Similar to NOTT-112, the exposed copper centers inside the cuboctahedral cages significantly contribute to their high H2 adsorption capacities at 77 K and 1 bar (2.39, 2.28 and 2.42 wt% for NOTT-113, NOTT-114 and NOTT-115, respectively). Of three MOFs studied, NOTT-115 exhibits the highest H2 uptakes at 77 K and 60 bar (6.7 wt% for NOTT-113, 6.8 wt% for NOTT-114 and 7.5 wt% for NOTT115), because NOTT-115 has the largest pore volume. However, NOTT-113 and NOTT-114 exhibit very similar H2 storage capacities, despite NOTT-114 having both a higher surface area and a larger pore volume than NOTT-113. This indicates that the amine-substituted central core leads to less favorable interaction with H2 than the other ligand systems studied. Comparison of the heat of H2 adsorption in the three MOFs (5.9 kJ mol1 for NOTT-113, 5.3 kJ mol1 for NOTT-114 and 5.8 kJ mol1 for NOTT-115 at zero coverage) also reveals that amine functionalization of the conjugated ligand core in NOTT114 does reduce the interaction energy between H2 and the framework, while functionalization of the central core of the hexagonal face with more aromatic rings increases H2–framework interactions. Independently, Zhou’s group134,136 also constructed an isoreticular series of rht-based MOFs PCN-61, PCN-66, PCN-68, which are made from the dicopper paddlewheel SBUs and hexatopic hexacarboxylic acids H6B3, H6B7, and H6B6, respectively. Virtually, PCN-61 and PCN-68 are the same as PMOF2(Cu) and NOTT-116, respectively. Generally, higher surface areas of isoreticular MOFs can be obtained by ligand extension but they tend to collapse upon activation; however, high BET surface areas were observed for PCN-61, PCN-66, and PCN-68, which the authors think is due to the fact that the formed cuboctahedra stabilized the frameworks by incorporating

5634 | Chem. Soc. Rev., 2014, 43, 5618--5656

Review Article

mesocavities with the microwindows. Of the three frameworks, PCN-61 has the smallest pore size and therefore exhibits the highest heat of H2 adsorption and the highest H2 adsorption capacity of 2.25 wt% at 77 K and 1 bar, which is in good agreement with that of PMOF-2(Cu). PCN-68 has the highest surface area and thus the highest total H2 uptake capacity of 13 wt% at 77 K and 100 bar. The total CH4 storage capacities at 298 K and 65 bar are 219, 187, and 187 cm3 (STP) cm3 for PCN61, PCN-66 and PCN-68, respectively. The total CO2 adsorption capacities at 298 K and 35 bar are 25.8, 28.9 and 34.2 mmol g1 for PCN-61, PCN-66 and PCN-68, respectively. Later on, the same group also synthesized one more (3,24)-connected rht-based mesoporous MOF PCN-69,132 also known as NOTT-119,131 via a solvothermal reaction of H6B14 and Cu(NO3)23H2O in DMF. The N2 sorption isotherm exhibits a pseudo type-I isotherm with a noticeable hysteresis, characteristic of a mesoporous MOF. Compared with PCN-68, PCN-69 has a lower BET surface area because of more pores distributing in the mesoporous range, despite a similar amount of adsorbed N2. Surprisingly, PCN-69 has a high heat of H2 adsorption (8.14 kJ mol1 at low coverage), presumably because the bent ligand creates pockets and concaves with improved binding affinity toward H2. However, the high pressure H2 uptake capacity in PCN-69 is not as good as PCN-68, indicating that a larger portion of mesoporosity is not good for high-pressure H2 storage. Interestingly, the gate-opening sorption behavior was observed, indicative of its framework flexibility. Such a framework flexibility originates from the pressure-responsive curvature change of the ligand adopted. A high gate opening pressure was observed in PCN-69, revealing that a higher energy is needed to trigger the curvature change, consistent with the origin of the framework flexibility. Solvothermal reaction of H6B10 and Cu(NO3)22.5H2O in DMF/EtOH/HCl at 353 K gave a rht-based MOF NU-111 (Fig. 10a).137,138 The N2 sorption isotherm reveals that NU-111 has a BET surface area of 5000 m2 g1, which is higher than that of PCN-69/NOTT-119, although the linker adopted in the latter is longer. This suggests that replacing the phenyl spacers of the organic linker with triple bond spacers can effectively

Fig. 10 (a) A portion of the (3,24)-connected rht-based framework of NU-111, and (b) high-pressure H2 sorption isotherms of NU-111 at 77 K. Reprinted with permission from ref. 137. Copyright 2012, American Chemical Society.


View Article Online


Review Article

boost the molecule accessible gravimetric surface areas of MOF. At 77 K and 110 bar, the total H2 uptake of NU-111 reaches up to 13.5 wt% (Fig. 10b). Also, NU-111 exhibits a significant CO2 adsorption of 38 mmol g1 at 298 K and 30 bar. The total CH4 uptake at 298 K and 65 bar by NU-111 reaches 0.36 g g1, corresponding to a volumetric uptake of 205 cm3 (STP) cm3. Both values are about 75% of the DOE’s new target for CH4 storage, indicating NU-111 is unique in its equally good volumetric and gravimetric uptakes. The CH4 storage working capacity, defined as the difference in uptakes between the pressures of 65 bar and 5 bar, is 177 cm3 (STP) cm3. Along this line, the same group synthesized two more new MOFs NU-109 and NU-110 using the organic linkers H6B11 and H6B9, respectively, which display the highest experimental BET surface area of any porous materials reported to date (7010 and 7140 m2 g1 for NU-109 and NU-110, respectively).139 To elucidate the effect of the amide groups upon CO2 adsorption, Zheng et al.140 constructed a rht-based MOF Cu-TPBTM based on dicopper paddlewheel SBUs and a hexacarboxylate ligand containing acylamide groups, 5,5 0 ,500 -[1,3,5benzenetriyltris(carbonylimino)]tris-1,3-benzene dicarboxylic acid (H6TPBTM, H6B18, Fig. 11a). The excess CO2 uptake reaches 330 cm3 (STP) cm3 at 298 K and 20 bar, approaching the performance of MIL-101 (MIL represents ‘‘Materials of Institut Lavoisier’’).141 Most remarkably, this MOF exhibits a stronger binding affinity for CO2 as well as a better CO2/N2 selectivity over the total pressure range measured (0–20 bar) than does the isostructural analogue PCN-61 (Fig. 11b). Note that this MOF and PCN-61 possess similar pore size, surface area, and the density of open copper sites, and the only difference between this MOF and PCN-61 is the substitution of the CRC moiety with an amide moiety. Thus, the better performance of this MOF in CO2 capture relative to PCN-61 is believed to be due to the large dipole–quadrupole interactions between the amide groups in this MOF and CO2 and/or NH OQCQO hydrogen bonds. To further demonstrate the advantages of amide groups for CO2 capture, the same group synthesized two expanded isoreticular rht-based MOFs ([Cu3(B19)] and [Cu3(B20)]) built from nanosized hexacarboxylate linkers H6B19 and H6B20.142 PXRD and gas sorption studies revealed that both materials are flexible, different from the parent MOF Cu-TPBTM. Despite the

Fig. 11 (a) A portion of the structure of the (3,24)-connected rht-based framework of Cu-TPBTM showing surface decoration by acylamide groups. (b) High pressure gravimetric excess CO2 and N2 sorption isotherms of Cu-TPBTM and the PCN-6x series at 298 K. Reprinted with permission from ref. 140. Copyright 2011, American Chemical Society.


Chem Soc Rev

fact that the surface of the MOF [Cu3(B20)] is decorated with nitrogen-containing triazine rings, it has almost the same gas sorption behavior as [Cu3(B19)]. At 273 K and 20 bar, the MOF [Cu3(B19)] takes up an exceptionally high excess CO2 uptake of 157 wt% but very limited amounts of CH4 (13 wt%) and N2 (11 wt%). The Henry’s law selectivities of CO2/CH4 and CO2/N2 for [Cu3(B19)] reach up to 8.6 and 34.3, much higher than the corresponding values of MOF-177 (4.4 and 17.5) and most other MOF materials, indicating that the introduction of amide groups into MOFs did enhance the adsorption selectivity. The results were further supported by Grand Canonical Monte Carlo (GCMC) simulations and the first principle calculations. GCMC simulations reveal that CO2 molecules in [Cu3(L19)] are mainly embedded in the relatively small cuboctahedral cage, and CO2 molecules prefer to locate at both the open copper sites and CONH groups within the framework. Moreover, the firstprinciple calculation indicates that the CO2 binding energy of the carbonyl sites is very comparable with that of open copper sites, while the CO2 affinity of the amide sites is significantly weaker than that of the carbonyl sites. So the studies highlight that immobilization of polar amide functionalities into frameworks might be an effective approach to enhance CO2 capture capacity and selectivity. In order to introduce nitrogen-rich units into highly porous MOFs for enhancing the gas uptake capacity, Li et al.143 constructed an rht-based MOF Cu-TDPAT built on a hexacarboxylate ligand with an imino triazine backbone, 2,4,6-tris(3,5-dicarboxylphenylamino)-1,3,5-triazine (H6TDPAT, H6B21) (Fig. 12a). Cu-TDPAT is the smallest member among (3,24)-connected rht-based MOFs reported to date, featuring a high density of both OMSs (1.76 nm3) and Lewis basic sites (LBSs, 3.52 nm3). Remarkably, such a dual functionalization of the framework, namely, concurrent incorporation of high density of OMSs and LBSs, results in its high CO2 uptake capacity and strong adsorption enthalpy for CO2, as well as high adsorption selectivity of CO2 over N2 at 298 K (Fig. 12b). At 298 K, the CO2 uptake amount is 132 and 31.3 cm3 g1 at 1.0 bar and 0.1 bar, respectively, substantially higher than all previously reported rhtbased structures. A very high adsorption enthalpy of 42.2 kJ mol1 at zero loading is clearly indicative of strong adsorbate–adsorbent interactions. The IAST CO2/N2 separation selectivity as high as 79 was achieved for a 10 : 90 CO2–N2 gas mixture at a total

Fig. 12 (a) A portion of the structure of the (3,24)-connected rht-based framework of Cu-TDPAT showing surface decoration by imino triazine moieties; and (b) CO2 and N2 sorption isotherms of Cu-TDPAT at 298 K. Reprinted with permission from ref. 143. Copyright 2012, Wiley.

Chem. Soc. Rev., 2014, 43, 5618--5656 | 5635

View Article Online


Chem Soc Rev

Fig. 13 (a) Three different cages in the crystal structure of NTU-105, and (b) CO2 (273 K), N2 (273 K) and H2 (77 K) adsorption isotherms of activated NTU-105. Reprinted with permission from ref. 145. Copyright 2013, Nature.

pressure of 1 atm, which was further confirmed by breakthrough experiments showing that Cu-TDPAT can effectively capture CO2 from the CO2–N2 mixed gas and can be fully regenerated under relatively mild conditions. In addition, Cu-TDPAT also shows extremely high gas uptake capacity under high pressure: total H2 of 6.77% at 77 K and 67 bar, total CH4 of 181 cm3 (STP) cm3 at 298 K and 35 bar, excess CO2 of 310 cm3 (STP) cm3 at 298 K and 48 bar. The same MOF was also synthesized by Eddaoudi et al. and named rht-MOF-7.144 But the conflict adsorption data were reported. For example, the CO2 uptake of rht-MOF-7 at 273 K and 1 bar is 146 cm3 g1, while that for Cu-TDPAT is 227 cm3 g1, which may be due to the degree of sample activation. Recently, Wang et al.145 synthesized a triazole-containing dendritic hexacarboxylate linker, 5,5 0 ,500 -4,4 0 ,400 -(benzene-1,3,5triyl)tris(1H-1,2,3-triazole-4,1-diyl)triisophthalic acid (H6B22), via ‘‘click’’ chemistry, and subsequently used it to successfully construct a highly porous nitrogen-rich rht-based MOF NTU105 incorporating accessible coordination-free triazole units (Fig. 13a). Different from the more usual fcc-packing in the prototypical rht-based net, the overall structure of NTU-105 is based on body centered tetragonal (bct) packing of cuboctahedra in 3D space. Likewise, three types of cages were formed within NTU-105, namely, cub-Oh, T-Td and T-Oh, with inner sphere diameters of 12, 15, and 20 Å, respectively. The three types of cages tessellate in the same way as in the rht-based network. Significantly, combination of the coordination-free triazole moieties and the accessible copper sites within the framework provides strong interactions with the gas molecules and thus achieves high gas adsorption capacities. The CO2 uptake capability reaches 187 cm3 g1 at 273 K and 1 atm (Fig. 13b), making NTU-105 a top MOF material for CO2 uptake reported to date.37 The isosteric heat of CO2 adsorption of 35 kJ mol1 at low-loading range is also quite high among the rht-based MOFs reported so far, just below the highest value of 42.2 kJ mol1 for Cu-TDPAT.143 Molecular simulation clearly revealed that not only open copper sites but also nitrogen-rich triazole units within the framework were the preferential interaction sites for CO2, responsible for the high and selective CO2 uptake. In addition, the desolvated NTU-105a also exhibits an exceptionally high H2 uptake capacity up to 2.75% at 77 K and 1 atm (Fig. 13b). To date, there are only a handful of MOFs with H2 uptakes exceeding 2.6% under the same conditions.32

5636 | Chem. Soc. Rev., 2014, 43, 5618--5656

Review Article

The same MOF was also reported by Hupp’s group146 and ¨der’s group147 independently, and named as NU-125 and Schro NOTT-122, respectively. In their reports, the high-pressure adsorption properties were investigated in detail. Taking NU-125 as an example, the maximum excess H2 uptake is about 6.0 wt% at 77 K, but only 1.0 wt% of absolute H2 uptake was observed at 298 K and 65 bar. NU-125 has an absolute CH4 storage capacity of 228 cm3 (STP) cm3 at 298 K and 58 bar, corresponding to 86% of the CH4 stored in a compressed natural gas (CNG) tank at 248 bar. Taking 5.8 bar as a specific lower pressure limit and 58 bar as the upper limit, the deliverable capacity of CH4 of NU-125 is 174 cm3 (STP) cm3 at 298 K. The CO2 uptake at 298 K and 30 bar is about 25 mmol g1. Different from most hexatopic carboxylates containing three coplanar isophthalate units used to construct rht-based MOFs, as discussed above, Sun et al. synthesized a series of C3-symmetric hexacarboxylate ligands (H6B15–H6B17) with three isophthalate units being non-coplanar.148 Interestingly, their solvothermal assembly with dicopper paddlewheel Cu2(COO)4 SBUs also resulted in the formation of three (3,24)-connected MOFs SDU-6-8 (SDU represents ‘‘Shandong University’’) with the same rht-based network as reported structures. Because the functional groups point toward the center of the T-Oh cage, the cavity size of the T-Oh cage decreases with the increase of the size of the inner functional groups. The cavity radius of the T-Oh cage changes from 6.0 Å in SDU-6, 5.6 Å in SDU-7 to 4.5 Å in SDU-8, respectively. However, the cub-Oh and T-Td cages are fixed in SDU-6-8 with the approximate cavity radius of 6.6 and 6.7 Å, respectively. Thus, this series of MOFs provides a great chance to systematically investigate the effect of the functional groups on the gas adsorption capacity. The desolvated materials SDU-6-8 take up 2.15, 2.13 and 2.03 wt% H2 at 77 K and 1 bar, respectively. The higher H2 uptake capacity of SDU-6 compared to the other two is attributed to its large surface area as well as the stronger polar hydroxyl group. In the low-pressure region (less than 0.27 bar), the H2 uptake of SDU-8 is slightly larger than SDU-7, which is due to the fact that the bulky functional group decreases the pore size and enhances the roughness of the pore surface. Due to the highest surface area of SDU-6, it has the highest maximum excess H2 uptake capacity of 5.73 wt%. The total gravimetric H2 uptakes of SDU-6-8 are 7.63, 7.16 and 6.45 wt% at 77 K and 55 bar, respectively. At 298 K and 35 bar, the total volumetric CH4 uptake capacities of SDU-6-8 are 172, 160 and 147 cm3 (STP) cm3, respectively. This study indicates that the polarity of the functional groups has a significant effect on the gas adsorption of an MOF, and decoration of the cage walls with strong polar groups can enhance the adsorption capacities for N2, H2 and CH4. A copper–hexacarboxylate framework UTSA-20 was constructed using a hexacarboxylic acid, 3,3 0 ,300 ,5,5 0 ,500 -benzene1,3,5-triyl-hexabenzoic acid (H6bhb, H6B1), exhibiting a novel topology of zyg instead of rht-related. This is because there exist steric hindrance and repulsion between the two closest axial ligands in the dicopper paddlewheel units in the two closest cuboctahedra if the suppositional rht-related network is formed. Two different types of 1D channels are formed within the


View Article Online


Review Article

Fig. 14 (a) Two different types of 1D channels within the framework UTSA-20 along the c axis with the potential open copper sites exposed to the pore surfaces: rectangular pores with dimensions of 3.4 4.8 Å and cylindrical pores with a diameter of 8.5 Å. (b) High-pressure excess CH4 sorption isotherms of UTSA-20 at various temperatures.

framework with the potential open copper sites exposed to the pore surfaces: rectangular pores with dimensions of 3.4 4.8 Å and cylindrical pores with a diameter of 8.5 Å (Fig. 14a). The framework exhibits the absolute volumetric CH4 storage capacity of 195 cm3 (STP) cm3 at 300 K and 35 bar (Fig. 14b).149 Computational investigations indicate that besides the open copper sites, the linker channel sites are also one of the primary CH4 adsorption sites, and that the CH4 binding at the linker channel sites is even stronger than that at OMSs because the CH4 molecule is well sandwiched between two bhb linker potential surfaces. The combination of the two adsorption sites (open copper sites and linker channel sites) contributes to B90% of the experimental uptake at 300 K and 35 bar. The remaining B10% may be easily attributed to additional secondary binding sites which exhibit lower heats of adsorption. The CH4 storage density of 0.222 g cm3 in micropores in UTSA-20 at 300 K and 35 bar is equivalent to the density of compressed CH4 at 300 K and 340 bar. Such high CH4 storage density is attributed to the full utilization of both open copper sites and the pore space. 3.2

Chem Soc Rev

1152 m2 g1, comparable to the largest surface areas ever reported in Ln-MOFs.152–154 Remarkably, NJU-Bai11a exhibits excellent adsorption capacity for CO2 (130 cm3 g1 at 273 K and 1 bar), and H2 (1.43 wt% at 77 K and 1 bar). The H2 adsorption enthalpy of 7.05 kJ mol1 is close to the highest value of 7.3 kJ mol1 reported among Ln-MOFs.155 The high enthalpy of CO2 adsorption of 30.3 kJ mol1 at zero coverage as well as the good separation selectivities of CO2 over CH4 and N2 clearly indicated the preferable affinity of the inserted amide groups in the structure towards CO2 than CH4 and N2, since no molecule sieving effect exists in NJU-Bai11 because the size of the open channel (8 Å) along the a direction is much bigger than that of gas molecules such as CO2 (3.3 Å), CH4 (3.8 Å), and N2 (3.64 Å). Recently, Shi et al. used the hexacarboxylate ligand H6B21 to construct a luminescent MOF Zn-TDPAT [Zn3(B21)(H2O)3] via a solvothermal reaction with Zn(NO3)26H2O.156 The X-ray single crystal diffraction results reveal that Zn-TDPAT has the same (3,24)-connected rht-based network as Cu-TDPAT (Fig. 15a). Most remarkably, this compound exhibited the significant luminescence quenching effect for nitrobenzene (Fig. 15b), and the luminescence intensities decrease monotonically with an increase in the concentrations of nitrobenzene (Fig. 15c). Such luminescence quenching is ascribed to the electron transfer from the benzene rings of the TDPAT ligand to electrondeficient nitrobenzene. The luminescence of Zn-TDPAT can be easily recovered by simply filtrating and washing several times with DMF. In addition, the luminescence intensity of Zn-TDPAT is enhanced linearly with decreasing temperature because cooling is gradually limiting the thermally activated intramolecular rotations and non-radiative decay (Fig. 15d). Thus, this compound can serve as a dual functional luminescent sensor for quantitatively detecting the concentration of nitrobenzene and temperature.

Other metal tri-isophthalate frameworks

Solvothermal assembly of H6B18 with zinc(II) ions generated a rht-based MOF.150 However, the sample lost its crystallinity and turned into a non-porous material after removal of the guest molecules, apparently due to the intrinsic instability of dizinc paddlewheel Zn2(COO)4 SBUs and the non-rigid ligand. In fact, a similar MOF PCN-60 constructed from the zinc paddlewheel SBUs and H6B3 ligands also suffers from such instability upon the removal of guest molecules.136 So, rigid ligands and stable paddlewheel clusters are necessary to stabilize the (3,24)connected rht-based MOFs. The same ligand H6B18 was also used by Bai et al. to synthesize a lanthanide MOF (Ln-MOF) NJU-Bai11 [Y2(B18)(H2O)2],151 crystallizing in a chiral space group P212121. Structurally, the carboxylate groups from B18 ligands bridge the Y3+ ions into a helical chain, which is further linked to eight neighboring helices by the B18 ligand to form a 3D network. There are open channels with a diameter of about 8 Å along the a direction. The activated NJU-Bai11a possesses a BET surface area of


Fig. 15 (a) Structure of Zn-TDPAT, (b) emission spectra of Zn-TDPAT in different solvents, aniline and nitrobenzene (excited at 370 nm), (c) concentration-dependent luminescence intensities of Zn-TDPAT by the addition of different contents of nitrobenzene in methanol (excited at 370 nm). (d) Temperature-dependent intensities of Zn-TDPAT at different temperatures (excited at 370 nm). Reproduced from ref. 156.

Chem. Soc. Rev., 2014, 43, 5618--5656 | 5637

View Article Online


Chem Soc Rev

Two 3D MOFs, Zn4O(B1) and Zn3(B1), are assembled from the hexacarboxylate ligand H6B1 with Zn(II) ions under different solvothermal conditions.157 The MOF Zn4O(B1) was composed of Zn4O(COO)6 clusters linked by B1 ligands to form a 3D framework with NaCl-type topology, while the MOF Zn3(B1) contains non-centrally symmetrical dinuclear SBUs which are connected by B1 ligands to generate a 3D network with a different cor based topology. Treatment of H6B1 ligands with Cd(NO3)24H2O afforded another MOF Cd3(B1). Compared with the MOF Zn3(B1), this Cd-based MOF contains two types of dinuclear SBUs which are further connected by B1 ligands to form a 3D network of the same cor-based topology. The activated MOF Zn4O(B1) exhibits a BET surface area of 156 m2 g1, and takes up 0.38 wt% of H2 at 77 K and 1 atm, and 35.0 cm3 g1 of CO2 and 10.8 cm3 g1 of CH4 at 273 K and 1 bar. However, the activated MOF Cd3(L1) did not take up any gas molecule, but adsorbed methanol of 6.5% at 298 K and 160 mbar, indicating that the activated sample might be partially recovered back into the original porous structure. Sun et al. synthesized a trimethyl substituted bhb ligand (H6tmbhb, H6B2) and constructed the corresponding zinc-based MOF SDU-1.158 Due to the introduction of the sterically congested methyl group on the linker, the carboxylate groups rotate to form a large dihedral angle with respect to the central phenyl ring, compared to those in the above two zinc based MOFs, thus resulting in the formation of a different network. This framework contains two kinds of SBUs, namely, [Zn2(COO)3] and [Zn2(COO)4]. Six [Zn2(COO)4] SBUs are linked together by 8 tmbhb ligands to form a trisoctahedron (Fig. 16a). Four [Zn2(COO)3] SBUs connect with 4 tmbhb ligands to form another cubic polyhedron (Fig. 16b). Two different kinds of polyhedra are packed into a complicated 3D framework. Topologically, the framework can be simplified in three different manners. If one takes [Zn2(COO)3] SBU and trisoctahedral SBB as 3- and 24-connected nodes, respectively, the resulting 3D framework is a (3,24) connected network with a rht topology. If [Zn2(COO)4] SBU and cubic SBB are treated as 4- and 12-connected nodes, respectively, the framework is a (4,12)-connected ftw network. If two kinds of SBUs and tmbhb ligand are regarded as 3-, 4-, and 6-connected nodes, respectively, this framework can be simplified to a novel (3,4,6)-connected network.

Fig. 16 Two types of polyhedral cages in SDU-1: (a) the trioctahedral cage and (b) the cubic cage.

5638 | Chem. Soc. Rev., 2014, 43, 5618--5656

Review Article

4. Multifunctional MOFs based on tetra-isophthalates Scheme 4 summarizes a variety of octacarboxylate linkers containing four isophthalate moieties at the end, which have been incorporated into porous MOFs. 4.1

Copper tetra-isophthalate frameworks

Lin et al. synthesized a series of chiral binaphthyl-based aromatics-rich octacarboxylic acids (H8C1–H8C3) and used them to construct an isoreticular family of highly porous and robust MOFs, which were obtained by treating the corresponding organic linkers with Cu(NO3)22.5H2O under solvothermal conditions.159 Structurally, the organic linker is linked to 8 dicopper paddlewheels via carboxylate groups to form a scu-based net where the dicopper paddlewheel and the ligand act as 4- and 8-conencted nodes, respectively (Fig. 17a and b). As expected, the open channel sizes along the (001) and (110) direction decrease with the increasing steric bulk of hydroxyl, ethoxyl and benzyloxy groups on the 2,2 0 -position of the binaphthyl moieties of the octacarboxylic acid bridging ligands (Fig. 17c–h). Notably, the high connectivity of the ligands has dramatically enhanced the framework stability against removal of guest molecules. The activated samples [Cu4C1], [Cu4C2] and [Cu4C3] exhibit the high BET surface areas of 2149, 2285 and 1605 m2 g1, respectively, and take up a large amount of H2 of 2.5 wt%, 2.1 wt% and 1.8 wt% at 77 K and 1 bar, respectively. Of three compounds, the compound [Cu4C3] exhibited the lowest H2 uptake of 1.8 wt% due to its smallest surface area and pore volume. Although the compound [Cu4C2] has a higher surface area than the compound [Cu4C1], it exhibits a much lower H2 uptake of 2.1 wt% presumably due to its larger pore size relative to the compound [Cu4C1]. This study highlights the bright promise of using bridging ligands of high connectivity to build highly stable and porous MOFs for gas uptake applications. Expanding this strategy, the same group synthesized a series of (4,8)-connected MOFs using the elongated chiral binaphthylderived aromatic-rich octacarboxylate ligands (H8C4–H8C6).160 The MOF ([Cu4C5]) crystallizes in orthorhombic C222 space group, while other two MOFs ([Cu4C4] and [Cu4C6]) crystallize in the tetragonal P4 space group, but they have very similar structural characteristics. Because of the elongated ligands, the three MOFs possess very large solvent accessible volumes. After freeze-drying treatment, the MOFs [Cu4C4], [Cu4C5] and [Cu4C6] exhibit BET surface areas of 1942, 2448, and 1189 m2 g1, respectively, which are however significantly lower than those calculated from single-crystal structures, indicating that the MOFs have undergone some framework distortion upon desolvation, which has also been confirmed by PXRD studies showing that many of the PXRD peaks of the evacuated samples have disappeared. The three MOFs take up a moderate amount of H2 of 1.7 wt%, 1.8 wt% and 1.4 wt% at 77 K and 1 atm, respectively. The studies indicate that the strategy of the high network connectivity is an effective route to stabilize MOFs with highly porous structures but some framework distortion still occurs when the bridging ligands become much longer.


View Article Online

Chem Soc Rev


Review Article

Scheme 4

The representative tetra-isophthalate ligands used to construct MOFs.

¨der et al. synthesized a tetrahedrally branched octaSchro carboxylate ligand (H8C8) and prepared a robust and highly porous metal–organic polyhedral framework NOTT-140 based on the scu net, which consists of four-connected Cu2(COO)4 paddlewheels bridged through eight-branched C8 linkers.161 The framework structure can be viewed as the alternate packing of two types of polyhedral cages A and B in 3D space. As shown in Fig. 18, cage A (5.5 Å in diameter) is an octahedron composed of 4 dicopper paddlewheels and 4 isophthalate units from two ligands. Cage B (8.9 Å in diameter) is a slightly distorted cuboctahedron composed of 8 dicopper paddlewheels and 4 isophthalate units. Each cage A is surrounded by 8 cage B units via the sharing of a triangular face and vice versa. The desolvated NOTT-140 exhibits a high BET surface area


of 2620 m2 g1, which is much larger than the values for other reported porous (4,8)-connected MOF materials.159 NOTT-140 adsorbs 2.5 wt% of H2 at 77 K and 1 bar. Such a high uptake at low pressure can be attributed to the high affinity of H2 for the open copper sites and the presence of the small octahedral cage A. The total H2 uptake of NOTT-140 reaches 6.0 wt% at 77 K and 20 bar, which is moderate compared with the highest capacity MOF materials. The isosteric heat of H2 adsorption at zero coverage is 4.15 kJ mol1, which is relatively low. The main reason is that the open copper sites in NOTT-140a are outside the cages, thus reducing the affinity between the framework and H2 molecules. At 293 K and 20 bar, CH4 and CO2 uptakes of NOTT-140a are 145 cm3 (STP) cm3 and 19.53 mmol g1, respectively.

Chem. Soc. Rev., 2014, 43, 5618--5656 | 5639

View Article Online


Chem Soc Rev

Review Article

Fig. 18 Views of the structure of NOTT-140. (a) Cage A, (b) Cage B, and (c) packing of two types of cages in 3D space.

Fig. 19 The small cage (a) and the large cage (b) in PCN-922. The alternate packing of these two cages along the c axis (c).

Fig. 17 (a) A view of dicopper [Cu2(COO)4] paddlewheels and their connectivity with the C1 ligand. (b) A simplified connectivity scheme showing the scu topology. Space filling models as viewed down the c axis and along the (110) direction for Cu4C1 (c and d), Cu4C2 (e and f) and Cu4C3 (g and h), respectively. Reprinted with permission from ref. 159. Copyright 2009, American Chemical Society.

A microporous MOF PCN-922 consisting of a dendritic octatopic organic linker H8ettb (H8C9) and dicopper paddlewheel SBUs, which could not be assembled directly from copper(II) salts and H8ettb, has been successfully synthesized by post-synthetic metathesis using a dizinc paddlewheel based MOF PCN-921 as a template.162 PCN-921 was easily obtained via a solvothermal reaction between H8ettb and Zn(NO3)26H2O in DEF in the presence of HBF4. Upon immersing PCN-921 in a DMF solution of Cu(NO3)2 at RT for 4 days, the zinc ions in PCN-921 could be completely replaced by copper ions, which was confirmed by X-ray photoelectron spectroscopy (XPS) and single-crystal XRD studies. In the structure of the resultant Cu-based MOF PCN-922, each ettb ligand connects 8 dicopper

5640 | Chem. Soc. Rev., 2014, 43, 5618--5656

paddlewheel SBUs in a rectangular prismatic arrangement, forming a highly porous (4,8)-connected 3D network of scu topology. The framework contains two types of microporous cages with different sizes. The small cage with the diameter of 14 Å is composed of 8 dicopper paddlewheel SBUs and 8 ettb linkers (Fig. 19a), while the large one with the diameter of 18 Å is formed by 8 dicopper paddlewheel SBUs and 12 ettb linkers (Fig. 19b). The two types of cages are arranged in an alternate fashion, forming 1D channels of 9 Å running along the c axis of the framework (Fig. 19c). After desolvation, PCN-921a hardly adsorbed any N2 gas, while PCN-922a exhibited a typical type-I N2 sorption isotherm, revealing the microporous nature of the framework with a BET surface area of 2006 m2 g1. Additionally, PCN-922a has very high H2 and CO2 uptake capacities under low pressure: 2.3 wt% of H2 at 77 K and 1 bar, and 81 cm3 g1 of CO2 at 298 K and 1 bar. Du et al. synthesized a tetrapodal octadentate ligand, 5,50 ,500 ,50 0 0 silanetetrayltetraisophthalic acid (H8C11), which is assembled with dicopper paddlewheels under solvothermal reaction conditions to generate a 3D porous (4,8)-connected MOF of scu based topology.163 There exist open channels of 4.7 6.3 Å2, 4.7 6.3 Å2 and 7.2 7.2 Å2 along the a, b and c axes, respectively. The guest solvent molecules can be only partially removed even by using the SCD method. The N2 adsorption isotherm reveals a type-I behavior with a BET surface area of 875 m2 g1. The H2 uptake capacity is 1.88 wt% at 77 K and 1 atm, which is moderately high. Additionally, the compound takes up different amounts of CO2 and CH4 (130 cm3 g1 of CO2 and 21 cm3 g1 of CH4 at 273 K and 1 atm), as a result of their different kinetic diameters and quadrupole moments. An octacarboxylate organic linker with condensed m-benzenedicarboxylate moieties, 1,2,4,5-tetra(5-isophthalic acid)benzene (H8C12), and its corresponding copper-based MOF UTSA-34


View Article Online


Review Article

were synthesized by our research group.164 UTSA-34 is a 3D framework in which 6 carboxylate groups of the ligand are connected to the dicopper paddlewheel SBUs. There exist large interconnected cages of about 12.8 Å in diameter that are surrounded by 24 isophthalates moieties. The pore structure can be regarded as a fcc close packing of spherical cages, each connected to 12 nearest neighboring cages. The desolvated UTSA-34 exhibits the promising potential for highly selective separation of C2 hydrocarbons from CH4, which was comprehensively examined by IAST and breakthrough calculations. UTSA-34 possesses higher separation capacity and selectivity than UTSA-33165 and the well investigated ZIF-8 (ZIF represents ‘‘zeolitic imidazolate framework’’).166 A robust MOF PCN-26 constructed from the flexible octacarboxylate ligand, tetrakis[(3,5-dicarboxyphenoxy) methyl]methane (H8C10), and dicopper paddlewheel Cu2(COO)4 SBUs was reported by Zhou et al. Solvothermal reaction of H8C10 with CuBr2 in DMF afforded this MOF.167 In the structure, PCN-26 contains two different kinds of cages. One is an octahedral cage in which four dicopper paddlewheel SBUs and two quaternary carbon atoms of two ligands occupy the vertices, and four CH2O–isophthalate moieties of the ligands occupy four faces (Fig. 20a). The other one is a cuboctahedral cage where eight dicopper paddlewheels and four quaternary carbon atoms occupy the 12 vertices (Fig. 20b). Every cuboctahedron is surrounded by 8 neighboring octahedra to form a polyhedronstacking 3D framework with open channels of 7.57 7.57, 8.13 8.13, and 7.93 7.93 Å2 along the a, b and c axes, respectively (Fig. 20c). Remarkably, the resulting MOF is rigid, although the flexible ligand is used. The N2 sorption isotherm revealed that the desolvated PCN-26 exhibited type-I sorption behavior with a BET surface area of 1733 m2 g1. PCN-26 adsorbs H2 of 2.57 wt% at 77 K and 1 atm, rising to 2.86 wt% at 77 K and 32.4 bar. Also, PCN-26 selectively adsorbs CO2 over CH4 and N2 at 298 K with the selectivities of 6.3 for CO2/CH4 and 21 for CO2/N2. The same MOF was also reported by Du et al.168 Due to the different activation methods, a lower BET surface area of 1115 m2 g1 and H2 uptake of 2.12 wt% at 77 K and 1 bar were observed. The C2H2 adsorption was also investigated. This MOF exhibits a high C2H2 uptake of 154 cm3 g1 at 296 K and 1 atm, comparable to that of MOF-50572 and Cu2(EBTC)71 despite a low surface area. Eddaoudi et al. used the octacarboxylate ligands (H8C14, H8C15, and H8C16, Scheme 4) to construct a family of isoreticular MOFs.169

Fig. 20 Views of the structure of PCN-26. (a) Octahedral cage, (b) cuboctahedral cage, and (c) two types of cages packed alternately in 3D space.


Chem Soc Rev

Fig. 21 Three types of polyhedral cages in the framework Cu-C14: (a) truncated tetrahedron, (b) truncated cube and (c) truncated cuboctahedron.

Solvothermal reaction of 5,5 0 ,500 ,5 0 0 0 -[1,2,4,5-phenyltetramethoxy]tetraisophthalate (H8C14) with Cu(NO3)22.5H2O yielded a crystalline material Cu-C14. The in situ formed dicopper paddlewheel units are bridged by 1,3-benzenedicarboxylate to form 2D Cu-(5-R-isophthalate) supermolecular building layers (SBLs), which are pillared via the 4-connected ligand cores to give rise to a 3D network of tbo topology, analogous to the prototypical HKUST-1.64 There exist three kinds of polyhedral cages in the framework, namely, truncated tetrahedron, truncated cube and truncated cuboctahedron, shown in Fig. 21. The largest truncated cuboctahedra are surrounded by 6 truncated cubes and 8 truncated tetrahedra. The truncated cubes are surrounded by 6 truncated cuboctahedra and 8 truncated tetrahedra. The truncated tetrahedra are surrounded by 4 truncated tetrahedra and 4 truncated cubes. When the ligand H6C15 is used instead, the MOF Cu-C15 with the same tbo topology was formed in which the two added pendant arms are not metal-coordinated, and point into the largest polyhedral cavities. As illustrated in MOF Cu-C16, the ligand extension expands the size of all the cages. Such an isoreticular tbo-derived MOFs series provides an excellent platform to evaluate the impact of pore size, shape and functionality on the gas sorption. Thus, the authors compared the gas sorption properties of MOFs Cu-C14 and Cu-C15. As expected, the Langmuir apparent surface area of 1490 m2 g1 for Cu-C15 is smaller than that of 2896 m2 g1 for Cu-C14. The presence of the uncoordinated carboxylate groups in the framework Cu-C15 leads to high adsorption heat over the entire studied range but negatively affects the gas uptake at high pressure. 4.2

Other metal tetra-isophthalate frameworks

Du et al.170 prepared a photoluminscent microporous anionic MOF [(Me2NH2)2In2C10] with a (4,8)-connected scu topology by solvothermal self-assembly of In(NO3)34.5H2O and H8C10 in DMF. There are two crystallographically independent In(III) ions in the asymmetric unit cell: one In(III) ion is six-coordinated by four oxygen atoms from two chelating carboxylate groups and two oxygen atoms from two monodentate carboxylate groups, while the other In(III) ion is eight-coordinated by eight oxygen atoms from four chelating carboxylate groups, but both In(III) ions serve as 4-connected nodes, which are bridged by the octacarboxylate to form an anionic open framework encapsulating charge balancing Me2NH2+ counterions and DMF and H2O guest molecules. Alternatively, the structure can be viewed

Chem. Soc. Rev., 2014, 43, 5618--5656 | 5641

View Article Online


Chem Soc Rev

Fig. 22 Views of the structure of [(Me2NH2)2In2C10]. (a) The octahedral cage, (b) the cuboctahedral cage, and (c) two types of cages packed alternately in 3D space.

as the alternate packing of two types of cages (Fig. 22c). The small cage is an octahedral cage with the diameter of 4.2 Å composed of 4 In(III) ions and 4 isophthalate units from two ligands (Fig. 22a). The large one is a slightly distorted cuboctahedral cage with the diameter of 8.8 Å composed of 8 In(III) ions and 4 isophthalate units (Fig. 22b). The permanent porosity was established by N2 sorption isotherm, exhibiting a BET surface area of 752 m2 g1. The desolvated MOF takes up 1.11 wt% of H2 at 77 K and 1 atm, and selectively adsorbs CO2 over CH4. In addition, this MOF exhibited a strong fluorescent emission peak at 360 nm upon excitation at 280 nm at RT, which is blue shifted compared to the free ligand. More interestingly, the emission intensities of this MOF varied upon contact with different solvents. Aromatic guest molecules with electrondonating groups such as toluene and p-xylene enhanced the emission intensity, while aromatic guest molecules with electronwithdrawing groups such as nitrobenzene, 1,3-dinitrobenzene and 2,4-dinitrotoluene significantly quenched the emission. Furthermore, this MOF is more sensitive towards nitrobenzene than 1,3-dinitrobenzene and 2,4-dinitrotoluene, which is due to the pore sieving effect allowing nitrobenzene to pass through but blocking 1,3-dinitrobenzene and 2,4-dinitrotoluene. The excellent fluorescence quenching response to nitroaromatics can be attributed to the electrostatic interactions between the anionic framework and the electron-deficient nitroaromatic analytes. Thus, this MOF can be regarded as an efficient porous material based sensor for detecting nitroaromatic explosives. The same MOF was also synthesized by Cao’s group.171 When the sample was activated using the SCD method, a larger BET surface area of 1555 m2 g1 and higher gas sorption capacities (1.49 wt% of H2 at 77 K and 1 bar, 56.2 cm3 g1 of CO2 and 13.2 cm3 g1 of CH4 at 298 K and 1 bar) were obtained, once again highlighting the significance of activation methods on controlling the porosities. Replacing DMF with DMA in the starting materials afforded another supramolecular isomer.172 In the asymmetric unit cell there exists only one crystallographically independent In(III) ion, which is coordinated by four chelating carboxylate groups to generate a mononuclear 4-connected [In(COO)4] node that is further linked by the octacarboxylate ligand to form a 3D (4,8)-connected anionic framework. There were two types of channels in the structure: one elliptical channel with a diameter of about 8.8 5.7 Å2 along the a or b axes, and another

5642 | Chem. Soc. Rev., 2014, 43, 5618--5656

Review Article

rectangular one with a diameter of about 5.8 5.7 Å2 along the c axis. The counterions Me2NH2+ can be completely postsynthetically exchanged with TMA+ (tetramethylammonium), TEA+ (tetraethylammonium) and TPA+ (tetrapropylammonium), while only half of the Me2NH2+ cations were replaced by TBA+ (tetrabutylammonium) even on prolonging the reaction time and increasing the concentration of TBA+. Remarkably, the resultant MOFs, labelled as A, B, C, D, exhibited distinctly different stabilities and gas sorption properties. For example, upon desolvation, the compound A loses its crystallinity while compounds B–D remain intact. The compound B shows typical type-I behavior with a BET surface area of 756 m2 g1. In contrast, no significant N2 adsorption was observed for the compound C, probably due to the TPA+ ions blocking the channels. Moreover, the compound D only adsorbs a small amount of N2, indicating that only part of the channels were blocked by TBA+ due to the partial exchange. Of particular interest is the fact that the compound C exhibits selective adsorption of CO2 and H2 but no N2, indicative of its potential applications in both H2 enrichment and CO2 capture. This study clearly indicates that gas sorption properties of the framework can be modulated by a judicious choice of the guest cations. Two isostructural porphyrin-based MOFs (MMPF-4 and MMPF-5) were synthesized by Ma et al.173 using a custom-designed porphyrin, tetrakis(3,5-dicarboxyphenyl)porphine (H10tdcpp, H8C13). Solvothermal reaction of the H10tdcpp ligand with Zn(NO3)2 and Cd(NO3)2, respectively, in DMSO at 408 K afforded single crystals of MMPF-4 and MMPF-5. In MMPF-4, eight [Zn2(COO)3] paddlewheels are linked by 6 in situ metallated porphyrin moieties Zn-tdcpp to form a small cubicuboctahedron serving as a SBB (Fig. 23a), which is connected with 6 adjacent SBBs through 6 Zn-tdcpp moieties to generate an augmented pcu network where each SBB is considered as a 6-connected node (Fig. 23b).

Fig. 23 (a) 6 square Zn-tdcpp MBBs are linked with 8 triangular Zn2(COO)3 MBBs to form a small cubicuboctahedron serving as a SBB in MMPF-4. (b) Zn-tdcpp ligands fuse the square faces of small cubicuboctahedra to afford an augmented pcu network. (c) The octahemioctahedral cage formed between the SBBs. Reproduced from ref. 173.


View Article Online


Review Article

In the assembly, another type of octahemioctahedral cage was also formed between the SBBs (Fig. 23c). Similarly, MMPF-5 is also based upon a small cubicuboctahedron SBB composed of six Cd-tdcpp moieties that are linked by 8 [Cd(COO)3] moieties. Remarkably, MMPF-4 exhibited high CO2 uptake capacity and excellent CO2/N2 adsorption selectivity. CO2 adsorption capacity at 1 atm reaches up to 124 cm3 g1 at 273 K and 67 cm3 g1 at 298 K. The IAST adsorption selectivity of CO2 over N2 is as high as 123 for a 15 : 85 CO2/N2 gas mixture at 273 K and 1 bar. In the crystal structure of MMPF-5, the Cd(II) cation residing within the porphyrin ring of the tdcpp ligand lies far out of the porphyrin plane, indicating the Cd(II) cations within the porphyrin macrocycle are readily substituted by other metal ions. Thus, upon immersing the crystals of MMPF-5 in the DMSO solution of Co(NO3)26H2O at 358 K for two days,174 the catalytically inactive Cd(II) based MMPF-5 was transformed into a catalytically active MOF MMPF-5(Co). Single-crystal X-ray diffraction studies revealed that all of the Cd(II) cations within the porphyrin macrocycles of tdcpp ligands are exclusively replaced by the Co(II) cations but the Cd(II) cations serving as the nodes in the framework remain intact. The catalytic performance of MMPF-5(Co) was evaluated in epoxidation of trans-stilbene using TBHP as oxidant in acetonitrile at 333 K. Control experiments showed that MMPF-5(Co) outperformed the homogeneous counterpart (cobalt(II) metallated tetrakis(3,5dicarboxymethylesterphenyl) porphine), and other Co(II) based MOFs examined such as MMPF-2118 and PPF-1Co119 in terms of both yield and selectivity. Furthermore, MMPF-5(Co) could be used for five cycles without a significant drop in its catalytic activity. Direct solvothermal reaction of the same ligand H8C13 with Co(NO3)26H2O in DMA at 388 K afforded another robust MOF MMPF-2.118 In the structure, there are two types of the ligands featuring bridging carboxylate groups and chelated carboxylate groups, respectively. Three cobalt atoms were bridged by the m3-OH group and six carboxylate groups from six different tdcpp ligands to form a distorted trigonal prismatic SBU. Each SBU links six tdcpp ligands and every ligand connects with 8 SBUs, forming a (6,8,8)-connected 3D network. Derived from the Ar adsorption isotherm data, MMPF-2 has a Langmuir surface area of 2037 m2 g1, which is the highest among reported porphyrin-based MOFs. Also, MMPF-2 has a CO2 uptake capacity of 101 cm3 g1 at 298 K and 1 atm, which is also among the highest yet reported for porous MOFs under the same conditions. Independently, Wu et al.175,176 incorporated octatopic metalloporphyrin ligands, metal 5,10,15,20-tetrakis(3,5-biscarboxylphenyl)porphyrin (M-H8OCPP, M-H8C13, M = Mn(III)Cl or Ni(II)), into three isostructural porous MOFs of tbo topology, namely, ZJU-18 ([Mn5Cl2(MnCl-OCPP)(DMF)4(H2O)4]2DMF8CH3COOH14H2O), ZJU-19 ([Mn5Cl2(Ni-OCPP)(H2O)8]7DMF6CH3COOH11H2O), ZJU-20 ([Cd5Cl2(MnCl-OCPP)(H2O)6]13DMF2CH3COOH9H2O), and examined their catalytic activities for oxidation of alkylbenzenes. Of these three MPFs, ZJU-18 consisting of Mn(III)porphyrin units coordinated to manganese containing SBUs


Chem Soc Rev Table 3

Selective oxidation of alkylbenzenes catalyzed by ZJU-18a

Entry Substrate

Product

Convension (%) Selectivity (%)

1

499

499

2

74

499

3

58

499

4

42

499

5

18

499

6

16

499

a

Alkybenzene (0.1 mmol), TBHP (0.15 mmol), catalyst (0.005 mmol), acetonitrile (1.0 mL), acetic acid (0.2 mL) and water (0.2 mL).

exhibited highly efficient and selective oxidation of alkylbenzene (Table 3). Furthermore, in terms of the catalytic activities, ZJU-18 is very superior to the molecular counterpart Mn(III)Cl-Me8OCPP, indicating that such a porous metalloporphyrinic framework enhanced their catalytic activities by blocking the formation of the catalytically inactive dimetalloporphyrinic species. A solvothermal reaction of CdCl22.5H2O and an octacarboxylate ligand H8C7 in DMF afforded a homochiral framework ocMOM-2 (ocMOMs represents ‘‘homochiral metal–organic materials that exhibit enantioselective organocatalysis’’).177 The Cd2+ ions are coordinated by four carboxylate groups from four different ligands to form a 4-connected node, which is further linked by 1,3-benzenedicarboxylate groups to yield a 2D layer containing triangles and pentagons. Ligand to ligand cross-linking of these sheets between the 5-positions of the 1,3-benezenedicarboxylate moieties afforded a 3D network with a new type of (4,8)-connected topology. Two types of channels were formed in the framework: 1.2 nm channels along the a axis and 0.8 nm along the b axis. The compound did not exhibit the permanent porosity even after activation using the SCD method. Since the permanent porosity is not the essential prerequisite for a heterogeneous catalysis in a solution, the compound might be useful for solution-based heterogeneous asymmetric catalysis applications.

Chem. Soc. Rev., 2014, 43, 5618--5656 | 5643

View Article Online

Chem Soc Rev

5. Comparison of diverse topologies of the MOFs constructed from meta-benzenedicarboxylate units


5.1

Terminology, definitions, and preliminaries

In this section, we are concerned with some aspects of the underlying topology of the structures of the MOFs of this review. The nets of MOFs with polytopic linkers were recently reviewed178 and just some major points relevant to the topic of this review and some nets that illustrate these points are recalled here. For the convenience of the reader, we first review some basic definitions and terminologies. The topology is described by a net which is an abstract graph that is simple (edges are undirected and there are no loops or multiple edges between vertices) and connected (there is a path of edges linking every pair of vertices).179 We like to distinguish between the abstract net which consists of vertices and edges, and the embedding of the graph which consists of nodes (or branch points) and links. In an embedding, coordinates are assigned to vertices and we can talk about such things as the length of a link, or the coordination figure (e.g. square or tetrahedron) of a node (It is clearly meaningless to talk about the length of an edge of an abstract graph). The nets we will be concerned with are crystallographic. This means that the combinatorial symmetry of the graph (its automorphism group) is isomorphic with a crystallographic space group which will be the maximum possible symmetry of an embedding in a crystal structure (excluding, of course, false apparent symmetry resulting from disorder in a crystal). Recognition of this simple fact would eliminate many wrong topology assignments. A graph with one topological kind of vertex (or edge) is called vertex (or edge) transitive. More generally we define a transitivity p q that indicates that there are p kinds of vertices and q kinds of edges. Thus, in a maximum symmetry embedding of a net with transitivity p q, the vertices fall into p groups with nodes in each group related by symmetry, but nodes in different groups not so related. Similarly there are q groups of links. A vertex that is common to k edges is referred to as k-coordinated (the term k-connected has a different meaning in graph theory, so is avoided) and often written k-c. If the net has both k-c and j-c vertices it is written as (k,j)-c. Some of the more important nets are collected in the RCSR database which, among other things, gives a maximum-symmetry embedding of the net.25 There they are assigned a symbol which may be three letters such as xyz or three letters plus an extension such as xyz-a. In particular the extension -a refers to an augmented net in which the nodes are replaced by their coordination figures. Here we focus on the structures of MOFs with the tetratopic, hexatopic, and octatopic linkers of Schemes 1–4. These can be considered either as one single node (4-c, 6-c or 8-c) of the underlying net as is often done and is generally the case in the proceeding sections. For example, the first such MOF with an assigned topology was probably MOF-505 with 4-c dicopper

5644 | Chem. Soc. Rev., 2014, 43, 5618--5656

Review Article

paddlewheels joined by a tetracarboxylate linker.65 For that material the topology was reported as nbo and that is certainly correct. But it is now realized that one needs to go further to completely characterize the topology. As shown below, the linkers under discussion contain 3-c branch points (nodes), and it is best to describe the topology using the 3-c branch points as nodes rather than considering the linker as just one node.178 In fact even better is to do both, to identify a basic net with the linker as a single node and a derived net with the 3-c nodes explicitly included. Some reasons for this are: (i) previous practice has been inconsistent. Thus the tetratopic linkers are almost always considered as single 4-c nodes, but hexatopic linkers are almost never considered as single 6-c nodes. (ii) There are generally more than one derived nets corresponding to a given basic net. If the derived net is not identified, fundamentally different topologies cannot be distinguished, and indeed have been confused in the past. (iii) The maximum possible symmetry of the framework is that of the derived net. For example the derived net may be intrinsically chiral whereas the basic net is not. (iv) The organic SBU contains two (or in general maybe more) links that can be independently varied in length. In the earlier review178 the Minimum Transitivity Principal was described. This states that ‘‘The underlying nets of MOFs and related materials tend to be nets of minimal transitivity’’. When linking two nodes the minimal edge transitivity is one and the basic nets of this type are now well documented.180 Now consider MOFs made with the linkers of Fig. 24. For the tetratopic linker in the derived net, there are at least two nodes (A and B) and two links (A–B and B–B); accordingly, the minimal transitivity is p q = 2 2. For the hexatopic linker in the

Fig. 24 The local topology of MOFs formed with polytopic linkers and one kind of metal SBU (magenta points labelled A). Green and red points are branch points of the linker. The linkers are (a) tetratopic, (b) hexatopic, (c) and (d) octatopic. Only topologies consistent with linkers containing meta-benzenedicarboxylate units are shown.


View Article Online


Review Article

Chem Soc Rev

derived net, there are three kinds of nodes (A, B and C) and two kinds of links (A–B and B–C), so the minimal transitivity is 3 2. In the octatopic case there are again three kinds of nodes but for links there are two possibilities. Either [Fig. 24(c)] A–B and B–C or [Fig. 24(d)] A–B, B–C and C–C; accordingly the minimal transitivity will be 3 2 or 3 3, respectively. The majority of the MOFs in this review have minimal transitivity nets and the discussion in this section is mainly restricted to them. Fig. 27

5.2

The basic 4-c net ssa and the (3,4)-c derived net sty.

MOFs with di-isophthalate tetratopic linkers

The most commonly observed topology has been found with essentially planar tetratopic linkers and the Cu2 paddlewheel SBUs. In most of these cases, the resulting topology is derived from the most-symmetrical net with planar 4-c nodes, namely nbo. However as explained above, the linker has two 3-c branch points and thus lower symmetry than that (4/mmm = D4h) at the vertex sites in the nbo net. Accordingly there are many possible derived nets of lower symmetry. The two simplest, which account for most of the observed structures, are fof (the topology of MOF-505) and fog. The two nets have the same

Fig. 25 Primitive cells of the nbo basic net (binary version) and the two derived nets fof and fog. The derived nets are obtained by splitting 4-c vertices of the basic nets into pairs of 3-c vertices (shown in red).

Fig. 26 Top: the binary version of the nbo net and the derived net tfb. Below, one cage in the structure with six red 4-c vertices.


Fig. 28 The basic net ssb and two derived minimal nets, stu and stx, found in MOFs.

symmetry (R3% m) and have generally not been distinguished in the literature. Of 25 MOFs of this type reported twenty have the fof topology and five the fog topology. A primitive cell for each of the structures is shown in Fig. 25. It is an interesting challenge for the theoretician to determine why one or the other of these two nets is found in real materials. Notice that the fog version has large open channels parallel to the rhombohedral c axis. Both fog and fof have a minimal transitivity of 2 2. A third (3,4)-c net, tfb, derived from nbo has also been found in tetracarboxylate MOFs with 4-c metal SBUs.115,116 The relation

Fig. 29 Part of the augmented net ntt-a showing three tertiary building units (TBUs) joined to a common 3-c vertex (shown as a blue triangle in the augmented net).

Chem. Soc. Rev., 2014, 43, 5618--5656 | 5645

View Article Online


Chem Soc Rev

Review Article

Fig. 30 The infinite TBU in the zyg net. The net is shown in augmented form with vertices replaced by vertex figures (squares and triangles in this case). The red squares correspond to the Cu2 paddlewheels in UTSA-20.

of the derived net to the basic net is illustrated in Fig. 26. This net again has a minimal transitivity of 2 2. As shown in the figure the structure contains cages surrounded by six 4-c linkers. These are arranged as in cubic closest packing (net fcu); hence the name fcu-MOF.116 Although the nbo net is the most symmetric and mostcommonly occurring topology for linking square nodes, there are several other possibilities. There are two other nets with transitivity 1 1 namely lvt and rhr which are occasionally found in MOFs though not in the materials of this review. Two binodal nets with transitivity 2 1 with nodes in square coordination have also been identified.181 We have not found them except as derived nets. The first ssa has symmetry P63/mmc and it appears that there is just one suitable way of replacing a 4-c node by two 3-c nodes keeping the full symmetry as shown in Fig. 27. The derived net, sty, is found in several materials of this review, specifically ZJU-2599 and PCN-12.88 The second net, ssb,

has symmetry I4/mmm and four derived nets can be made with the same symmetry. Two of these are shown in Fig. 28. One stx is found in NOTT-109 for which the crystal structure has the same symmetry. NOTT-109 was previously assigned the pts topology and it is worth seeing why that could not be the case. pts has symmetry P42/mmc with four 4-c nodes in the unit cell. The structure of NOTT-109 has symmetry I4/mmm with 16 4-c nodes in the unit cell. For the topology to be pts, I4/mmm would have to be a subgroup of index four of P42/mmc. A quick glance at the International tables for Crystallography will show that this is not the case. The MOF named MMPF-1 is isoreticular with NOTT-109 (i.e. stx again).87 However, the topology was again misassigned by the authors, this time to lvt. Again consideration of symmetry shows this assignment to be impossible. lvt has symmetry I41/amd, but the crystal has symmetry I4/m. For the underlying net to be lvt I4/m would have to be a subgroup of index two of I41/amd. Again a glance at the Tables shows that this is not the case. A MOF with a tetracarboxylate linker, benzenetetrabenzoate (not an isophthalate), has the other ssb derived topology, stu. So again we have different derived topologies from the same basic net. 5.3

MOFs with tri-isophthalate hexatopic linkers

By far, the largest numbers of MOFs with hexatopic linkers have the linker topology shown in Fig. 24 joining Cu2 paddlewheel SBUs. The underlying topology has been described in a number of ways including uninodal, binodal and trinodal nets. The most common approach, indicated above is to identify a tertiary building unit (TBU) of 12 linked paddlewheels in a cuboctahedral arrangement. This TBU is joined to 24 3-c branch points to form the (3,24)-c net rht. This description was first given by

Table 4 C2H2 adsorption of porous MOFs constructed from the organic linkers containing m-benzenedicarboxylate units at RT and 1 atm. For comparison, HKUST-1 and MOF-74 are included

C2H2 adsorption MOFs

Dc (g cm3)

CoMOF-74 MnMOF-74 HKUST-1 FeMOF-74 MgMOF-74 NOTT-109 ZnMOF-74 UTSA-20 ZJU-5 MOF-505 Cu4(tdm) NOTT-103 NOTT-101 Cu2(ebtc) ZJU-25 UTSA-40 UTSA-34b NOTT-102 UTSA-33 ZJU-26 Cu2(bbtc)

1.169 1.085 0.879 1.126 0.909 0.790 1.231 0.910 0.679 0.927 0.833 0.643 0.684 0.718 0.622 0.827 0.840 0.587 0.993 0.615 0.601

Vp (cm3 g1)

0.760 0.630 0.850 0.675 1.074 0.677 0.612 1.157 1.080 1.000 1.183 0.650 0.542 1.268 0.367 0.572 0.574

BET

cm3 (STP) cm3

cm3 (STP) g1

Qst (kJ mol1)

Ref.

1018 695 1401 1350 927 2110 747 1706 2823 1139 1152 2958 2805 1852 2124 1630 991 3342 660 989 1014

230 182 177 176 167 161 150 136 131 137 128 128 126 115 109 103 102 86 83 52 50

197 168 201 156 184 204 122 150 193 148 154 199 184 160 175 125 121 146 84 84 84

50.1 39.0 34.0 47.0 34.0 29.5 24.0 30.8 35.8 24.7

102 102 72 61 102 187 102 149 101 187 168 187 187 71 100 76 164 187 165 188 74

30.8 37.1 34.5 25.4 40.7 50.0 22.0 33.9 32.7 37.6

Dc: framework density; Vp: pore volume; BET: BET surface area; tdm = tetrakis[(3,5-dicarboxyphenyl)oxamethyl]methane; ebtc = 1,1 0 -ethynebenzene-3,3 0 ,5,5 0 -tetracarboxylate; bbtc = 1,1 0 -butadiynebenzene-3,3 0 ,5,5 0 -tetracarboxylate.

5646 | Chem. Soc. Rev., 2014, 43, 5618--5656


View Article Online

Review Article

Chem Soc Rev

Table 5 CH4 adsorption of some porous MOFs constructed from the organic linkers containing m-benzenedicarboxylate units. For comparison, HKUST-1 and NiMOF-74 are included

CH4 adsorption


MOF HKUST-1 NiMOF-74 PCN-14 NJU-Bai10 NOTT-109 MOF-505 PCN-11 NOTT-101 NOTT-103 PCN-16 ZJU-5 NU-135 UTSA-20 NU-125 NOTT-102 Cu-TDPAT ZJU-25 SDU-6 PCN-46 PCN-61 UTSA-34b SDU-7 PMOF-3 NOTT-140 UTSA-40 HNUST-3 SDU-8 NU-111 PCN-66 NOTT-122 PCN-68 SNU-50 NPC-5 PCN-16 0 NOTT-119 NJU-Bai12 HNUST-2 HNUST-1 Cu3B18

Dc (g cm3)

Vp (cm3 g1)

BET

Total cm3 cm3

Deliverable cm3 cm3

0.883 1.206 0.829 0.871 0.668 0.7899 0.9265 0.7485 0.6838 0.6432 0.7235 0.679 0.751 0.909 0.578 0.5872 0.782 0.622 0.611 0.618 0.56 0.840 0.606 0.882 0.677 0.8270 0.6983 0.639 0.409 0.45 0.589 0.38 0.650 0.822 0.7641 0.361 0.522 0.570 0.580 0.407

0.78 0.51 0.85 0.87 1.11 0.850 0.677 0.91 1.08 1.157 1.06 1.074 1.02 0.66 1.29 1.268 0.93 1.183 1.17 1.012 1.36 0.542 1.10 0.718 1.07 0.65 0.99 1.02 2.09 1.63 1.41 2.13 1.08 0.496 0.84 2.35 1.135 0.97 0.571 1.77

1850 1350 2000 1753 2883 2110 1661 1931 2805 2958 2273 2823 2530 1620 3120 3342 1938 2124 2826 2500 3000 991 2713 1840 2620 1630 2412 2516 4930 4000 3286 5109 2300 1140 1760 4118 3038 2366 1400 3288

227 228 195 230 199 196 195 194 194 193 191 190 187 184 182 181 181 180 172 172 171 159 159 159 159 156 149 147 138 136 132.1 128 126 124 111 106 100 96 94 91

150 106 122 107 125 104 125 138 140 134 130 127 124 133 136 122 132 127 132 127 99 114 101 102 105 111 101 98 70 86

CH4 adsorption T (K)

P (bar)

298 298 298 290 290 300 300 298 300 300 300 300 298 298 298 300 298 300 298 298 298 290 298 298 293 300 298 298 298 298 298 298 298 293 300 298 298 298 298 273

35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 20 35 20 35 35 35 20 35 35 20 35 35 20 20 20 20

Total cm3 cm3

Deliverable cm3 cm3

T (K)

P (bar)

267 251 230

190 129 157

298 298 298

65 65 65

242 230 235 239 236

170 139 166 183 183

300 300 298 300 300

65 65 60 65 65

228 230 230 232 237 222 229

168 170 170 183 192 163 181

300 298 298 298 300 298 300

65 65 65 65 65 65 63

206 219

166 174

298 298

65 65

192

138

300

65

206 187

179 152

298 298 298

65 65

187

157

298

65

Qst (kJ mol1) 17.0 21.4 18.7 30.0 14.9 17.1 18.2 14.6 15.5 15.9 15.3 16.5 17.7 15.5 16.0 15.1

16.6 15.4 15.0

26.8 16.1 154

134

298

65 15.7 15.0 23.4

Ref. 146 146 146 95 85 99 99 70 99 99 73 101 104 149 146 99 143 100 148 189 134 164 148 94 161 76 82 148 190 134 147 134 75 191 73 131 79 80 81 142

Dc: framework density; Vp: pore volume; BET: BET surface area; the deliverable amount is defined as the difference in total uptake between 5 bar and the specified upper limiting working pressure at the isothermal condition; TDPAT = 2,4,6-tris(3,5-dicarboxylphenylamino)-1,3,5-triazine.

Eddaoudi et al. for a compound with a tritopic linker joining 3-c and 4-c metal SBUs and appropriate in that case as in fact the 3-c branch point.178 A similar description was also given for the same topology, now with a hexacarboxylate linker by Lah et al.150 It might be noted that the cuboctahedral TBU is the same as MOP-1 (Fig. 1) and is also illustrated in Fig. 29. As some authors have remarked, the pattern of metal SBUs (4-c nodes in the (3,4)-c net) alone is that of the uninodal 5-c net ubt. For reasons given above we prefer a description that recognizes explicitly the 4-c paddlewheel SBU and the individual 3-c branch points of the linker as originally suggested by Eddaoudi et al. in their supplementary material.178 This gives the (3,4)-c net with the RCSR symbol ntt. A fragment of the net in augmented form (vertices replaced by vertex figures, in this case triangles and squares) in which three TBUs joined to a


common 3-c vertex is shown in Fig. 29. The (3,4) net is a minimal transitivity (3 2) net. Interestingly, no author has described the net as (4,6)-c with the linker considered as a single 6-c node. As remarked previously,179 that net would be noncrystallographic (have nonrigid body symmetries). The ntt net requires essentially planar hexacarboxylate linkers. With a linker too small to allow planarity linking square paddlewheels, a different topology is found in UTSA-20.149 The linker has an overall trigonal prismatic shape and if the linker is considered a 6-c node the net is the basic net stp for linking square and trigonal prismatic SBUs. The (3,4)-c derived net taking the 3-c branch points of the linker as nodes is zyg. In this case, the TBU is an infinite column of paddlewheels as shown in Fig. 30 which might be compared with Fig. 29. zyg, like ntt, is a minimal transitivity net.

Chem. Soc. Rev., 2014, 43, 5618--5656 | 5647

View Article Online


Summary of H2 adsorption data of porous MOFs constructed from the organic linkers containing m-benzenedicarboxylate units

MOF


Review Article

PCN-12 UTSA-20 SNU-5 NTU-105 PCN-14 Cu3Cr(tstc) PCN-308 NOTT-110 NOTT-103 PCN-307 UHM-4 NOTT-122 UHM-3 PCN-16 NOTT-100 Cu2(ebtc) PCN-26 NOTT-111 PCN-11 NOTT-101 NOTT-105 PCN-306 Cu4C1 NOTT-140 NJU-Bai10 MOF-505 NOTT-115 PCN-12 0 NOTT-113 Cu4C14 PCN-10 NOTT-109 NOTT-112 PCN-922 PMOF-2(Cu) NOTT-106 UHM-2 NOTT-114 NOTT-107 PCN-61 NOTT-102 PCN-305 HNUST-3 UTSA-40a Cu4C10 SDU-6 SNU-50 NU-111 Cu4C2 NOTT-400 HNUST-1 SDU-7 PMOF-3 SNU-4 SDU-8 Cu2TPTC-OnPr PCN-46 NJU-Bai12 NOTT-116 PCN-68 NU-100 UHM-6 Cu4(H4C15) Cu4C3 Cu4C5 Cu2(TPTC-OEt) PCN-66 NTU-101-Cu PCN-16 0

Surface area (m2 g1) Dc Vp (g cm3) (cm3 g1) BET Langmuir

Total H2 adsorption H2 adsorption Qst at 77 K/1 bara (wt%) wt%a g L1 T (K) P (bar) (kJ mol1) Ref.

0.762 0.910 0.768 0.598 0.829 0.706

3.05 2.9 2.87 2.75 2.70 2.70 2.67 2.64 2.63 2.62 2.62 2.61 2.60 2.60 2.59 2.58 2.57 2.56 2.55 2.52 2.52 2.50 2.50 2.50 2.49 2.47 2.42 2.40 2.39 2.37 2.34 2.33 2.3 2.3 2.29 2.29 2.28 2.28 2.26 2.25 2.24 2.20 2.2 2.2 2.12 2.15 2.10 2.1 2.1 2.14 2.14 2.13 2.12 2.07 2.03 1.96 1.95 1.91 1.90 1.87 1.82 1.8 1.80 1.8 1.8 1.79 1.79 1.78 1.7

0.614 0.643 0.589 0.618 0.927 0.718 0.839 0.617 0.749 0.684 0.730 0.727 0.677 0.668 0.927 0.611 0.851 0.592 0.706 0.767 0.790 0.503 0.666 0.559 0.720 0.574 0.560 0.587 0.691 0.698 0.827 0.833 0.611 0.650 0.409 0.703 1.025 0.580 0.606 0.882 1.020 0.639 0.619 0.522 0.407 0.380 0.279 0.965 0.928 0.814 0.564 0.450 0.764

0.94 0.63 1.00 1.33 0.878 1.086 0.810 1.22 1.142 0.808 1.41 1.152 1.06 0.680 1.008 0.84 1.19 0.91 0.886 0.898 1.043 0.9765 1.07 1.11 0.63 1.38 0.73 1.25 0.97 0.67 0.705 1.62 0.94 1.485 0.798 1.36 0.767 1.36 1.138 0.926 0.99 0.65 0.612 1.17 1.08 2.09 1.051 0.56 0.571 1.10 0.727 0.53 1.02 0.593 1.012 1.135 2.17 2.13 2.82 0.593 0.47 0.706 0.97 0.576 1.63 0.814 0.84

1943 1156 3543 1753 2485 1418 2960 2929 1376 1360 3286 2430 2273 1640 1852 1733 2930 1931 2316 2387 1927 2149 2620 2883 3394 1577 2970 1407 1718 3800 2006 3730 1855 1692 3424 1822 3000 2942 1720 2412 1630 1115 2826 2300 4930 2285 1350 1400 2713 1840 2516 1396 2500 3038 4664 5109 6143 1164 1605 2448 1293 4000 2017 1760

5648 | Chem. Soc. Rev., 2014, 43, 5618--5656

2425 1783 2850 2793 2234 2235

2800 2844 2385 2442 2929 2486 3108 1830 1962 2896 1779 2615 4180

3500 2599 2784 1662 1722 2450 2650 1620 2020 1460 1658 2800 3208 6033 1490 1841 2819 1612 4600 2200

4.40 6.76

40.1 51.9

77 77

15 50

5.42 6.03

44.9 42.6

77 77

35 60

7.62 7.78

46.8 50.0

77 77

55 60

7.0

41.2

77

20

5.85 4.02 5.66 3.74 7.36 5.97 6.60 5.40

36.2 37.2 40.6 31.4 45.4 44.7 45.1 39.4

77 77 77 77 77 77 77 77

25 20 20 32.4 48 45 60 20

6.0 10.49

40.6 70.1

77 77

20 100

4.15 6.3

8.07

49.3

77

60

5.8

7.17

42.5

77

60

5.23 4.15 10.0

39.2 32.8 50.3

77 77 77

45 20 77

5.9 6.8 6.8

7.0 4.50

39.2 32.4

77 77

50 20

7.24 4.46 7.71 7.20

41.6 43.2 42.3

77 77 77 77

60 20 33 60

6.1 4.62

41.8 38.2

77 77

20 65

7.63 7.85 12

46.6 51.0 49

77 77 77

55 60 65

6.43 7.1 5.0

3.84

39.4

77

20

5.96

7.16 3.87 4.49 6.45

43.5 34.1 45.8 39.2

77 77 77 77

55 20 50 55

5.84 8.9 7.24 6.25

7.39 6.27 10.1 10.83 16.4

45.7 32.7 41.1 41.1 45.7

77 77 77 77 77

97 20 50 50 70

7.20 6.8 6.7 6.09 6.1 8.0 7.6

9.07

40.8

77

45

6.22

3.62

27.7

77

25

11.60 6.61 8.6 8.4 6.48 5.68 5.71 6.24 8.1 6.0 7.9 6.3 6.81 6.21 7.0 5.3 5.77 6.37

5.64 9.2 7.6 5.3 6.70 6.36 5.4 6.47 6.38

88 149 69 145 192 112 84 68 67 84 91 147 92 32 66 and 67 71 167 68 70 66 and 67 67 84 159 161 85 65 135 88 135 169 70 67 128 162 126 67 91 135 67 134 66 and 67 84 82 76 168 148 75 190 159 109 81 148 94 69 148 193 189 79 129 134 133 93 169 159 160 193 134 83 32


View Article Online

Review Article Table 6

(continued)

MOF


Chem Soc Rev

Cu4C4 NOTT-205 Cu2(bddc) Cu2(TPTC-OMe) [In2(tdm)](Me2NH2)2 Cu2(TPTC-OnHex) HNUST-2 NJU-Bai11 Cu4C6 NOTT-204 NOTT-209 CPF-1 Cu2(Ru(CO)-ddcpp) Cu2(Mn-ddcpp) Cu2(Ni-ddcpp) NOTT-201 NOTT-208 NOTT-200 NOTT-207 Cu2(Zn-ddcpp) NOTT-206 Cu2(Pd-ddcpp) NU-135 JUC-62 Cu-tdpat NOTT-119 NU-125 NPC-5

Surface area (m2 g1) Dc Vp (g cm3) (cm3 g1) BET Langmuir

Total H2 adsorption H2 adsorption Qst a at 77 K/1 bar (wt%) wt%a g L1 T (K) P (bar) (kJ mol1) Ref.

0.572 0.847 0.602

1.7 1.66 1.64 1.57 1.49 1.48 1.45 1.43 1.4 1.39 1.31 1.29 1.16 1.05 1.03 1.02 0.99 0.96 0.89 0.81 0.73 0.55

0.751

0.77 0.419 1.113 0.5045 0.62 0.453 0.97 0.464 0.47 0.326 0.303 0.311 0.328 0.225 0.286 0.239 0.287 0.136 0.206 0.204 0 0.157 1.02

1942 1024 2357 1127 1555 1083 2366 1152 1189 820 729 548 810 509 647 580 687 180 474 498 3 379 2530

0.782 0.361 0.578 0.822

0.93 2.35 1.29 0.496

1938 4118 3120 1140

0.838 0.570 1.032 0.613 0.927 1.047 0.865

1.165 1.110 1.212 1.241 0.876 1.256

2245 3111 1414 1707 1269 2746 1293 1323 853 968 680 864

613 486 2608 1395

2.88 4.82

24.4 43

77 77

20 31

6.13 6.9

4.26

35.7

77

30

6.15

5.20

30.3

77

20

6.23 7.05

2.36 2.11

21.9 22.1

77 77

20 20

7.57 12.04

1.88 1.75 1.33 1.30

21.9 19.4 16.1 16.1

77 77 77 77

20 20 20 20

10.10 8.73 9.03 9.13

1.09

13.7

77

20

7.81

49

77 77 77 77 77 77

55 40 67 60 60 20

5.6

6.52 4.71b 6.77 10.1 8.0 3.4

52.8 37 46.2

7.3 5.3

160 105 194 193 171 193 80 151 160 105 106 110 195 195 195 108 106 108 106 195 106 195 104 196 143 131 146 191

Dc: framework density; Vp: pore volume; BET: BET surface area; tstc = trans-stilbene-3,3 0 ,5,5 0 -tetracarboxylate; ebtc = 1,1 0 -ethynebenzene-3,3 0 ,5,5 0 tetracarboxylate; TPTC-OEt = 2 0 ,5 0 -diethoxy-[1,1 0 : 4 0 ,100 -terphenyl]-3,300 ,5,500 -tetracarboxylate; bddc = 5,5 0 -(butadiyne-1,4-diyl) diisophthalate; TPTC-OMe = 2 0 ,5 0 -dimethoxy-[1,1 0 : 4 0 ,100 -terphenyl]-3,300 ,5,500 -tetracarboxylate; TPTC-OnHex = 2 0 ,5 0 -di-n-hexyloxy-[1,1 0 :4 0 ,100 -terphenyl]-3,300 ,5,500 tetracarboxylic acid; tdm = tetrakis[(3,5-dicarboxyphenyl)oxamethyl]methane; ddcpp = 5,15-bis(dicarboxyphenyl)porphyrin; tdpat = 2,4,6-tris(3,5dicarboxylphenylamino)-1,3,5-triazine. a 100 (weight of adsorbed H2)/(weight of host). b Excess uptake.

An interesting topology was found in JUC-100 (JUC represents ‘‘Jilin University China’’) in which a hexacarboxylate linker joined Zn4 SBUs with six octahedrally-arranged points of extension. Taking the linker as a 6-c node the net is that of NaCl (the binary version of the primitive cubic net pcu). However including the 3-c branch points of the linker as 3-c nodes one finds the derived net zxc. This is in fact just the positions of the atoms in calcite, CaCO3 with Ca bonded to six O, and C bonded to 3 O (so O is bonded to C + 2Ca).178 Clearly in calcite we want to consider the three atoms explicitly, rather than as a NaCl packing of Ca and CO3 groups (although that is not wrong); likewise it is more informative to consider the three nodes of the net explicitly. This is again a minimal transitivity (3 2) net.

6. Comparison of the MOFs constructed from m-benzenedicarboxylate units with others for their gas storage (H2, CH4 and C2H2) and carbon dioxide capture Table 4 summarizes crystal densities, pore volumes, BET surface areas and C2H2 adsorption of some porous MOFs constructed from the organic linkers containing the m-benzenedicarboxylate unit. Among these MOFs, NOTT-109 performs the best in terms


of gravimetric and volumetric C2H2 adsorption capacities at RT and 1 atm. The gravimetric uptake is the highest among all MOFs reported for C2H2 adsorption, while the volumetric one is only lower than those of HKUST-1 and MOF-74 series. As established in HKUST-1 in which each open copper site binds one C2H2 molecule, the copper site density of 3.45 mmol g1 in NOTT-109 can contribute 77.4 cm3 storage capacity of the total 204 cm3 at 1 atm and 296 K. The remaining C2H2 can be stored inside the pore space of moderate sizes within NOTT-109. The CH4 storage properties of some porous MOFs constructed from the organic linkers containing m-benzenedicarboxylate units are summarized in Table 5. The well investigated MOFs HKUST-1 and NiMOF-74 were also included. It can be seen that a few MOFs exhibit excellent methane adsorption properties. For example, at RT and 65 bar, NOTT-101, NOTT-102, NOTT-103, and NU-125 show the methane uptakes over 230 cm3 (STP) cm3 and the deliverable amounts higher than 190 cm3 (STP) cm3. At RT and 35 bar, NOTT-101 and NOTT-103 exhibit the methane uptakes higher than 190 cm3 (STP) cm3 and the deliverable amounts higher than 135 cm3 (STP) cm3. To date, HKUST-1 is the best-performing MOF material for volumetric CH4 storage and delivery. Table 6 lists the H2 adsorption capacities at low and high pressures for some porous MOFs constructed from the organic linkers containing m-benzenedicarboxylate units. PCN-12, UTSA-20,

Chem. Soc. Rev., 2014, 43, 5618--5656 | 5649

View Article Online


Review Article

Summary of CO2 adsorption data of porous MOFs constructed from the organic linkers containing m-benzenedicarboxylate units

Low-pressure CO2 adsorption High-pressure CO2 adsorption


MOFs Cu-TDPAT Cu2(dbip) Cu-TPBTM PCN-26 NOTT-122 MMPF-2 Cu4(C14) NTU-105 HNUST-1 rht-MOF-7 HNUST-3 PCN-922 NU-135 SNU-50 PCN-308 PCN-305 PCN-307 UTSA-40 PCN-306 MMPF-4 Cu4(H4C15) NJU-Bai11 [In2(tdm)](Me2NH2)2 NTU-101-Cu UHM-6 ZJU-26 CPF-1 NU-100 NU-111 PCN-68 PCN-66 Cu3BTB PCN-61 NU-125 PCN-46 NJU-Bai10 NJU-Bai12 NOTT-140a HNUST-2 UTSA-20 PMOF-3 NPC-5

Dc Vp Uptake (g cm3) (cm3 g1) BET (wt%) 0.782 0.768 0.627 0.839 0.589 0.902 0.706 0.598 0.579 0.788 0.698 0.666 0.751 0.650 0.691 0.827 0.768 0.928 1.032 0.838 0.965 0.615 0.865 0.279 0.409 0.380 0.450 0.407 0.560 0.578 0.618 0.668 0.522 0.677 0.570 0.910 0.882 0.822

0.93 0.81 1.268 0.84 1.41 0.61 0.97 1.33 0.571 0.76 0.99 0.94 1.02 1.08 0.808 1.043 0.810 0.65 0.926 0.47 0.464 0.62 0.813 0.593 0.572 0.311 2.82 2.09 2.13 1.63 1.77 1.36 1.29 1.012 1.11 1.135 1.07 0.97 0.63 0.727 0.496

1938 1773 3160 1733 3286 1410 3543 1400 2412 2006 2530 2300 1376 1927 1418 1630 1720 958 1152 1555 2017 1164 989 548 6143 4930 5109 4000 3288 3000 3120 2500 2883 3038 2620 2366 1156 1840 1140

25.8 24.0 23.3 21.4 20.4 19.8 18.9 18.4 18.3 17.6 16.6 15.9 15.5 15.7 15.4 14.5 14.4 14.4 13.8 13.2 12.9 12.9 11.0 9.6 9.2 7.46 6.2

T (K)

P (bar)

298 298 298 298 298 298 298 298 298

1.01 0.95 1 1.07 1 1.01 1.01 1.01 1

298 298 298 298 297 297 297 296 297 298 298 298 298 298 298 298 298

1 1 1 1.01 1 1 1 1.07 1 1.07 1.01 1 1 1.01 1 1.01 1.01

Gravimetric Volumetric Qst uptake (mg g1) uptake (cm3 cm3) T (K) P (bar) (kJ mol1) Ref. 892

355

298

48

1086

347

298

20

1182

355

298

20

680

244

298

25

496

146

298

20

929

330

298

20

814 770

311 255

298 298

30 55

559

236

300

30

372

176

298

25

2315 1680 1504 1284 1180 1140 1100 989 947 918 903 834 698 632 496

329 350 291 294 245 325 324 311 322 244 311 242 323 284

298 298 298 298 298 298 298 298 298 298 293 298 300 298 293

40 30 35 35 20 35 30 30 40 20 20 20 35 40 20

42.2 28.1 26.3 24.5 31 29.7 35 31.2 44.7 24.8 25.5 25.8 22.215 23.847 22.836 24 23.997 35.3 30.3 21.14 25 30 38.6 22 24.1 18.7 23.5 24.7 23.5 24.2

143 89 140 167 147 118 169 145 81 144 82 162 104 75 84 84 84 76 84 173 169 151 171 83 93 188 110 133 190 134 134 197 134 146 189 85 79 161 80 149 94 191

Dc: framework density; Vp: pore volume; BET: BET surface area; TDPAT = 2,4,6-tris(3,5-dicarboxylphenylamino)-1,3,5-triazine; dbip = 5-(3,5dicarboxybenzyloxy)isophthalate; TPBTM = N,N0 ,N00 -tris(isophthalyl)-1,3,5-benzenetricarboxamide; tdm = tetrakis[(3,5-dicarboxyphenyl)oxamethyl]methane.

and SNU-5 have H2 uptakes over 2.8 wt% at 77 K and 1 bar. The high pressure H2 adsorption capacities of some MOFs have surpassed 10 wt% at 77 K. These MOFs include NJU-Bai10, PCN-68, NOTT-112, NOTT-119, and NU-100. Apparently, the higher is the porosity of the MOFs, the higher is its H2 storage capacity under high pressure and 77 K. Those MOFs with small pore spaces, specific binding sites and moderate surface areas are favourable to their high H2 uptake at 77 K and 1 bar. We also summarize in Table 7 the CO2 adsorption capacities of some porous MOFs constructed from the organic linkers containing m-benzenedicarboxylate units. Again, their high pressure saturated CO2 adsorption capacities are linearly related to their porosities (BET surface areas), while those exhibiting high CO2 uptakes at RT and 1 atm, as demonstrated in PCN-26, Cu-TDPAT and NOTT-122, Cu-TPBTM, and Cu2(dbip), need to have specific sites for their enhanced interactions with CO2 molecules.

5650 | Chem. Soc. Rev., 2014, 43, 5618--5656

7. Recent development in the exploration of expanded m-benzenedicarboxylate units for the construction of highly porous MOFs Due to the power of the basic m-benzenedicarboxylate organic building subunits to construct highly porous MOFs, as discussed above, several expanded versions of m-benzenedicarboxylate units shown in Scheme 5 were developed. For example, Kong et al.182 synthesized two tricarboxylate organic linkers (H3D1 and H3D2, see Scheme 5) containing the expanded organic building subunits II and III, which are self-assembled with dicopper paddlewheel Cu2(COO)4 SBUs to form two highly porous MOFs ZJU-35 and ZJU-36, respectively. Their structures are isoreticular with HKUST-1, although the two linkers adopted are less symmetrical


View Article Online


Review Article

Scheme 5

Chem Soc Rev

The expanded organic building subunits and the corresponding organic linkers based on these subunits.

than H3btc. The expanded ligands resulted in the enlarged pores. High-pressure gas sorption isotherms indicate that both MOFs can take up a large amount of CH4 and CO2 at RT, and thus exhibit high potential for high-pressure swing adsorption (PSA) purification of H2. C3-symmetrical tri-isophthalates are assembled with paddlewheel units to usually form a (3,24)-connected rht-based network, which is based on 3-connected MBBs and 24-connected cuboctahedral SBBs. The latter consist of 12 paddlewheel units joined by 24 isophthalates. To enlarge the cuboctahedral SBB, Eddaoudi et al.183 synthesized

an organic linker (H6D3, Scheme 5) incorporating the expanded organic building subunits IV in which longer benzoate moieties replace the carboxylates of m-benzenedicarboxylate, and constructed the corresponding (3,24)-connected rht-based networks. The expanded isophthalate evidently enlarged SBBs with a diameter of 25.7 Å, almost double the size of the original SBB built from isophthalate moieties (Fig. 31). It should be mentioned that in addition to m-benzenedicarboxylate subunits, carbazole-3,6-dicarboxyaltes featuring a 901-bridging angle between carboxylate groups are being

Fig. 31 Cuboctahedral SBBs formed by 12 paddlewheels joined by 24 m-benzenedicarboxylates (I) or its expanded versions (II and IV). Octahedral SBBs formed by 6 paddlewheels joined by 12 carbazole-3,6-dicarboxyaltes (V).


Chem. Soc. Rev., 2014, 43, 5618--5656 | 5651

View Article Online


Chem Soc Rev

explored as new organic building subunits (V, Scheme 5). Zhou et al.184,185 designed the organic linkers (H8D4, H4D5 and H4D6, Scheme 5) incorporating such organic building subunits, and realized highly porous MOFs PCN-80, PCN-81 and PCN-82, respectively. It is well known that 12 carbazole-3,6-dicarboxylate ligands and 6 dicopper paddlewheel clusters are easily assembled into a discrete octahedral cage (Fig. 31).186 Such octahedral cages serving as 12-conencted nodes were observed in PCN-81 and PCN-82, but not in PCN-80. Evidently, the incorporation of these new organic building subunits with rich organic aromatic backbones will certainly lead to an abundance of new organic linkers for construction of highly porous MOFs in the near future.

8. Conclusion and outlook The development of new organic linkers is still very important to target functional MOF materials. Among the diverse basic units, the meta-benzenedicarboxylate one, summarized in this review, is particularly of importance to be developed into a number of organic linkers and thus MOFs of diverse structures and tuneable pores. The tuneable structures and porosities within this series of synthesized MOFs have enabled them to have wide applications on gas storage, gas separation, heterogeneous catalysis and sensing. The fact that some MOFs summarized here exhibit extraordinarily high gas storage/capture capacities for H2, CH4, C2H2 and CO2 indicates that a few very promising ones might be practically implemented in our daily lives in the near future. The richness of organic backbones will not only enrich the database of organic linkers containing metabenzenedicarboxylate units, but will also lead to some even better MOFs for the above mentioned applications. Future research will also be focused on the self-assembly of other metal ions/metal clusters with the developed organic linkers from meta-benzenedicarboxylate units to construct porous MOFs and then to explore their diverse functions. Of course, as mentioned in Section 7, other types of expanded m-benzenedicarboxylate units will also be extensively explored for their construction of functional MOFs in the near future.

Acknowledgements This work was supported by an AX-1730 grant from Welch Foundation (BC), and the National Natural Science foundation of China (No. 21301156).

Notes and references 1 S. A. Allison and R. M. Barrer, J. Chem. Soc. A, 1969, 1717–1723. 2 Y. Kinoshita, I. Matsubara, T. Higuchi and Y. Saito, Bull. Chem. Soc. Jpn., 1959, 32, 1221–1226. 3 A. Corma, F. Rey, J. Rius, M. J. Sabater and S. Valencia, Nature, 2004, 431, 287–290. ãs, J. L. Jorda ´, C. Martıńez and 4 A. Corma, M. J. Dıáz-Caban M. Moliner, Nature, 2006, 443, 842–845.

5652 | Chem. Soc. Rev., 2014, 43, 5618--5656

Review Article

5 H. J. Buser, D. Schwarzenbach, W. Petter and A. Ludi, Inorg. Chem., 1977, 11, 2704–2710. 6 S. S. Kaye and J. R. Long, J. Am. Chem. Soc., 2005, 127, 6506–6507. 7 P. K. Thallapally, R. K. Motkuri, C. A. Fernandez, B. P. McGrail and G. S. Behrooz, Inorg. Chem., 2010, 49, 4909–4915. 8 S. T. Wilson, B. M. Lok, C. A. Messina, T. R. Cannan and E. M. Flanigen, J. Am. Chem. Soc., 1982, 104, 1146–1147. 9 R. E. Morris, A. Burton, L. M. Bull and S. I. Zones, Chem. Mater., 2004, 16, 2844–2851. 10 E. R. Cooper, C. D. Andrews, P. S. Wheatley, P. B. Webb, P. Wormald and R. E. Morris, Nature, 2004, 430, 1012–1016. 11 T. Jiang, A. Lough, G. A. Ozin, R. L. Bedard and R. Broach, J. Mater. Chem., 1998, 8, 721–732. 12 B. F. Hoskins and R. Robson, J. Am. Chem. Soc., 1989, 111, 5962–5964. 13 B. F. Hoskins and R. Robson, J. Am. Chem. Soc., 1990, 112, 1546–1554. 14 B. F. Abrahams, B. F. Hoskins and R. Robson, J. Chem. Soc., Chem. Commun., 1990, 60–61. 15 R. W. Gable, B. F. Hoskins and R. Robson, J. Chem. Soc., Chem. Commun., 1990, 762–763. 16 M. Kondo, T. Yoshitomi, K. Seki, H. Matsuzaka and S. Kitagawa, Angew. Chem., Int. Ed. Engl., 1997, 36, 1725–1727. 17 H. Li, M. Eddaoudi, M. O’Keeffe and O. M. Yaghi, Nature, 1999, 402, 276–279. 18 M. Eddaoudi, J. Kim, N. Rosi, D. Vodak, J. Wachter, M. O’Keeffe and O. M. Yaghi, Science, 2002, 295, 469–472. 19 M. Yaghi and H. Li, J. Am. Chem. Soc., 1995, 117, 10401–10402. 20 O. M. Yaghi, G. Li and H. Li, Nature, 1995, 378, 703–706. 21 S. R. Batten, N. R. Champness, X.-M. Chen, J. Garcia¨ hrstro ¨m, M. O’Keeffe, M. P. Suhh Martinez, S. Kitagawa, L. O and J. Reedijk, CrystEngComm, 2012, 14, 3001–3004. 22 B. Chen, M. Eddaoudi, S. T. Hyde, M. O’Keeffe and O. M. Yaghi, Science, 2001, 291, 1021–1023. 23 M. Eddaoudi, D. B. Moler, H. Li, B. Chen, T. M. Reineke, M. O’Keeffe and O. M. Yaghi, Acc. Chem. Res., 2001, 34, 319–330. 24 O. M. Yaghi, M. O’Keeffe, N. W. Ockwig, H. K. Chae, M. Eddaoudi and J. Kim, Nature, 2003, 423, 705–714. 25 M. O’Keeffe, M. A. Peskov, S. J. Ramsden and O. M. Yaghi, Acc. Chem. Res., 2008, 41, 1782–1789. ´s, M. O’Keeffe 26 D. J. Tranchemontagne, J. L. Mendoza-Corte and O. M. Yaghi, Chem. Soc. Rev., 2009, 38, 1257–1283. ´rez, J. Kim, Y. Go, M. Eddaoudi, 27 H. K. Chae, D. Y. Siberio-Pe A. J. Matzger, M. O’Keeffe and O. M. Yaghi, Nature, 2004, 427, 523–527. 28 H. Furukawa, N. Ko, Y. B. Go, N. Aratani, S. B. Choi, ¨ . Yazaydin, R. Q. Snurr, M. O’Keeffe, J. Kim E. Choi, A. O and O. M. Yaghi, Science, 2010, 329, 424–428. 29 S. Kitagawa, R. Kitaura and S.-I. Noro, Angew. Chem., Int. Ed., 2004, 43, 2334–2375. 30 S. Ma and H.-C. Zhou, Chem. Commun., 2010, 46, 44–53. ¨der, Top. Curr. 31 X. Lin, N. R. Champness and M. Schro Chem., 2010, 293, 35–76.


View Article Online


Review Article

32 M. P. Suh, H. J. Park, T. K. Prasad and D.-W. Lim, Chem. Rev., 2012, 112, 782–835. 33 T. A. Makal, J.-R. Li, W. Lu and H.-C. Zhou, Chem. Soc. Rev., 2012, 41, 7761–7779. 34 Y. He, W. Zhou, R. Krishna and B. Chen, Chem. Commun., 2012, 48, 11813–11831. 35 H. Wu, Q. Gong, D. H. Olson and J. Li, Chem. Rev., 2012, 112, 836–868. 36 J.-R. Li, J. Sculley and H.-C. Zhou, Chem. Rev., 2012, 112, 869–932. 37 K. Sumida, D. L. Rogow, J. A. Mason, T. M. McDonald, E. D. Bloch, Z. R. Herm, T.-H. Bae and J. R. Long, Chem. Rev., 2012, 112, 724–781. 38 J. Lee, O. K. Farha, J. Roberts, K. A. Scheidt, S. T. Nguyen and J. T. Hupp, Chem. Soc. Rev., 2009, 38, 1450–1459. 39 L. Ma, C. Abney and W. Lin, Chem. Soc. Rev., 2009, 38, 1248–1256. ¨nker, K. Gedrich and 40 G. Nickerl, A. Henschel, R. Gru S. Kaskel, Chem. Ing. Tech., 2011, 83, 90–103. 41 M. Yoon, R. Srirambalaji and K. Kim, Chem. Rev., 2012, 112, 1196–1231. 42 L. E. Kreno, K. Leong, O. K. Farha, M. Allendorf, R. P. V. Duyne and J. T. Hupp, Chem. Rev., 2012, 112, 1105–1125. 43 Y. Cui, Y. Yue, G. Qian and B. Chen, Chem. Rev., 2012, 112, 1126–1162. 44 P. Horcajada, R. Gref, T. Baati, P. K. Allan, G. Maurin, ´rey, R. E. Morris and C. Serre, Chem. Rev., P. Couvreur, G. Fe 2012, 112, 1232–1268. 45 B. Chen, S. Xiang and G. Qian, Acc. Chem. Res., 2010, 43, 1115–1124. 46 H.-L. Jiang and Q. Xu, Chem. Commun., 2011, 47, 3351–3370. 47 C. Wang, D. Liu and W. Lin, J. Am. Chem. Soc., 2013, 135, 13222–13234. 48 J. S. Seo, D. Whang, H. Lee, S. I. Jun, J. Oh, Y. J. Jeon and K. Kim, Nature, 2000, 404, 982–986. 49 O. R. Evans, H. L. Ngo and W. Lin, J. Am. Chem. Soc., 2001, 123, 10395–10396. 50 N. L. Rosi, J. Eckert, M. Eddaoudi, D. T. Vodak, J. Kim, M. O’Keeffe and O. M. Yaghi, Science, 2003, 300, 1127–1129. 51 X. Zhao, B. Xiao, A. J. Fletcher, K. M. Thomas, D. Bradshaw and M. J. Rosseinsky, Science, 2004, 306, 1012–1015. 52 R. Matsuda, R. Kitaura, S. Kitagawa, Y. Kubota, R. V. Belosludov, T. C. Kobayashi, H. Sakamoto, T. Chiba, M. Takata, Y. Kawazoe and Y. Mita, Nature, 2005, 436, 238–241. 53 B. Chen, C. Liang, J. Yang, D. S. Contreras, Y. L. Clancy, E. B. Lobkovsky, O. M. Yaghi and S. Dai, Angew. Chem., Int. Ed., 2006, 45, 1390–1393. 54 B. Chen, Y. Yang, F. Zapata, G. Lin, G. Qian and E. B. Lobkovsky, Adv. Mater., 2007, 19, 1693–1696. 55 A. Lan, K. Li, H. Wu, D. H. Olson, T. J. Emge, W. Ki, M. Hong and J. Li, Angew. Chem., Int. Ed., 2009, 48, 2334–2338. 56 S. Chen, J. Zhang, T. Wu, P. Feng and X. Bu, J. Am. Chem. Soc., 2009, 131, 16027–16029.


Chem Soc Rev

57 J.-P. Zhang and X.-M. Chen, J. Am. Chem. Soc., 2009, 131, 5516–5521. 58 H. Wu, W. Zhou and T. Yildirim, J. Am. Chem. Soc., 2009, 131, 4995–5000. 59 R. Vaidhyanathan, S. S. Iremonger, G. K. H. Shimizu, P. G. Boyd, S. Alavi and T. K. Woo, Science, 2010, 330, 650–653. 60 J. An, S. J. Geib and N. L. Rosi, J. Am. Chem. Soc., 2010, 132, 38–39. 61 E. D. Bloch, W. L. Queen, R. Krishna, J. M. Zadrozny, C. M. Brown and J. R. Long, Science, 2012, 335, 1606–1610. 62 M. Eddaoudi, J. Kim, J. B. Wachter, H. K. Chae, M. O’Keeffe and O. M. Yaghi, J. Am. Chem. Soc., 2001, 123, 4368–4369. 63 B. Moulton, J. Lu, A. Mondal and M. J. Zaworotko, Chem. Commun., 2001, 863–864. 64 S. S.-Y. Chui, S. M.-F. Lo, J. P. H. Charmant, A. G. Orpen and I. D. Williams, Science, 1999, 283, 1148–1150. 65 B. Chen, N. W. Ockwig, A. R. Millward, D. S. Contreras and O. M. Yaghi, Angew. Chem., Int. Ed., 2005, 44, 4745–4749. 66 X. Lin, J. Jia, X. Zhao, K. M. Thomas, A. J. Blake, G. S. ¨der, Walker, N. R. Champness, P. Hubberstey and M. Schro Angew. Chem., Int. Ed., 2006, 45, 7358–7364. 67 X. Lin, I. Telepeni, A. J. Blake, A. Dailly, C. M. Brown, J. M. Simmons, M. Zoppi, G. S. Walker, K. M. Thomas, ¨der, T. J. Mays, P. Hubberstey, N. R. Champness and M. Schro J. Am. Chem. Soc., 2009, 131, 2159–2171. 68 S. Yang, X. Lin, A. Dailly, A. J. Blake, P. Hubberstey, ¨der, Chem. – Eur. J., 2009, N. R. Champness and M. Schro 15, 4829–4835. 69 Y.-G. Lee, H. R. Moon, Y. E. Cheon and M. P. Suh, Angew. Chem., Int. Ed., 2008, 47, 7741–7745. 70 X.-S. Wang, S. Ma, K. Rauch, J. M. Simmons, D. Yuan, ´pez, A. D. Meijere X. Wang, T. Yildirim, W. C. Cole, J. J. Lo and H.-C. Zhou, Chem. Mater., 2008, 20, 3145–3152. 71 Y. Hu, S. Xiang, W. Zhang, Z. Zhang, L. Wang, J. Bai and B. Chen, Chem. Commun., 2009, 7551–7553. 72 S. Xiang, W. Zhou, J. M. Gallegos, Y. Liu and B. Chen, J. Am. Chem. Soc., 2009, 131, 12415–12419. 73 D. Sun, S. Ma, J. M. Simmons, J.-R. Li, D. Yuan and H.-C. Zhou, Chem. Commun., 2010, 46, 1329–1331. 74 L. Wang, L. Zhai, X. Ren and W. Zhang, J. Solid State Chem., 2013, 204, 53–58. 75 T. K. Prasad, D. H. Hong and M. P. Suh, Chem. – Eur. J., 2010, 16, 14043–14050. 76 Y. He, S. Xiang, Z. Zhang, S. Xiong, C. Wu, W. Zhou, T. Yildirim, R. Krishna and B. Chen, J. Mater. Chem. A, 2013, 1, 2543–2551. 77 Z. R. Herm, J. A. Swisher, B. Smit, R. Krishna and J. R. Long, J. Am. Chem. Soc., 2011, 133, 5664–5667. 78 H. Wu, K. Yao, Y. Zhu, B. Li, Z. Shi, R. Krishna and J. Li, J. Phys. Chem. C, 2012, 116, 16609–16618. 79 B. Zheng, R. Yun, J. Bai, Z. Lu, L. Du and Y. Li, Inorg. Chem., 2013, 52, 2823–2829. 80 Z. Wang, B. Zheng, H. Liu, P. Yi, X. Li, X. Yu and R. Yun, Dalton Trans., 2013, 42, 11304–11311.

Chem. Soc. Rev., 2014, 43, 5618--5656 | 5653

View Article Online


Chem Soc Rev

81 B. Zheng, H. Liu, Z. Wang, X. Yu, P. Yia and J. Bai, CrystEngComm, 2013, 15, 3517–3520. 82 Z. Wang, B. Zheng, H. Liu, X. Lin, X. Yu, P. Yi and R. Yun, Cryst. Growth Des., 2013, 13, 5001–5006. 83 X.-J. Wang, P.-Z. Li, L. Liu, Q. Zhang, P. Borah, J. D. Wong, X. X. Chan, G. Rakesh, Y. Li and Y. Zhao, Chem. Commun., 2012, 48, 10286–10288. 84 Y. Liu, J.-R. Li, W. M. Verdegaal, T.-F. Liu and H.-C. Zhou, Chem. – Eur. J., 2013, 19, 5637–5643. 85 Z. Lu, L. Du, K. Tang and J. Bai, Cryst. Growth Des., 2013, 13, 2252–2255. 86 C. Zou and C.-D. Wu, Dalton Trans., 2012, 41, 3879–3888. 87 X.-S. Wang, L. Meng, Q. Cheng, C. Kim, L. Wojtas, M. Chrzanowski, Y.-S. Chen, X. P. Zhang and S. Ma, J. Am. Chem. Soc., 2011, 133, 16322–16325. 88 X.-S. Wang, S. Ma, P. M. Forster, D. Yuan, J. Eckert, J. J. Lpez, B. J. Murphy, J. B. Parise and H.-C. Zhou, Angew. Chem., Int. Ed., 2008, 47, 7263–7266. 89 Z. Liang, J. Du, L. Sun, J. Xu, Y. Mu, Y. Li, J. Yu and R. Xu, Inorg. Chem., 2013, 52, 10720–10722. 90 R. Patra, H. M. Titi and I. Goldberg, CrystEngComm, 2013, 15, 2853–2862. ¨ba, 91 S. E. Wenzel, M. Fischer, F. Hoffmann and M. Fro J. Mater. Chem., 2012, 22, 10294–10302. ¨ba, Inorg. 92 S. E. Wenzel, M. Fischer, F. Hoffmann and M. Fro Chem., 2009, 48, 6559–6565. ¨ba, Inorg. 93 D. Frahm, M. Fischer, F. Hoffmann and M. Fro Chem., 2011, 50, 11055–11063. 94 X. Liu, M. Park, S. Hong, M. Oh, J. W. Yoon, J.-S. Chang and M. S. Lah, Inorg. Chem., 2009, 48, 11507–11509. 95 S. Ma, D. Sun, J. M. Simmons, C. D. Collier, D. Yuan and H.-C. Zhou, J. Am. Chem. Soc., 2008, 130, 1012–1016. 96 Y. Peng, V. Krungleviciute, I. Eryazici, J. T. Hupp, O. K. Farha and T. Yildirim, J. Am. Chem. Soc., 2013, 135, 11887–11894. 97 J. A. Mason, M. Veenstra and J. R. Long, Chem. Sci., 2014, 5, 32–51. 98 C. E. Wilmer, M. Leaf, C. Y. Lee, O. K. Farha, B. G. Hauser, J. T. Hupp and R. Q. Snurr, Nat. Chem., 2012, 4, 83–89. 99 Y. He, W. Zhou, T. Yildirim and B. Chen, Energy Environ. Sci., 2013, 6, 2735–2744. 100 X. Duan, J. Yu, J. Cai, Y. He, C. Wu, W. Zhou, T. Yildirim, Z. Zhang, S. Xiang, M. O’Keeffe, B. Chen and G. Qian, Chem. Commun., 2013, 49, 2043–2045. 101 X. Rao, J. Cai, J. Yu, Y. He, C. Wu, W. Zhou, T. Yildirim, B. Chen and G. Qian, Chem. Commun., 2013, 49, 6719–6721. 102 S. Xiang, W. Zhou, Z. Zhang, M. A. Green, Y. Liu and B. Chen, Angew. Chem., Int. Ed., 2010, 49, 4615–4618. 103 See DOE MOVE program at https://arpa-e-foa.energy.gov/. 104 R. D. Kennedy, V. Krungleviciute, D. J. Clingerman, J. E. Mondloch, Y. Peng, C. E. Wilmer, A. A. Sarjeant, R. Q. Snurr, J. T. Hupp, T. Yildirim, O. K. Farha and C. A. Mirkin, Chem. Mater., 2013, 25, 3539–3543. 105 S. Yang, X. Lin, A. J. Blake, K. M. Thomas, P. Hubberstey, ¨der, Chem. Commun., 2008, N. R. Champness and M. Schro 6108–6110.

5654 | Chem. Soc. Rev., 2014, 43, 5618--5656

Review Article

106 S. Yang, S. K. Callear, A. J. Ramirez-Cuesta, W. I. F. David, ¨der, J. Sun, A. J. Blake, N. R. Champness and M. Schro Faraday Discuss., 2011, 151, 19–36. 107 S. Yang, G. S. B. Martin, J. J. Titman, A. J. Blake, D. R. Allan, ¨der, Inorg. Chem., 2011, 50, N. R. Champness and M. Schro 9374–9384. 108 S. Yang, X. Lin, A. J. Blake, G. S. Walker, P. Hubberstey, ¨der, Nat. Chem., 2009, 1, N. R. Champness and M. Schro 487–493. 109 I. A. Ibarra, S. Yang, X. Lin, A. J. Blake, P. J. Rizkallah, H. Nowell, D. R. Allan, N. R. Champness, P. Hubberstey ¨der, Chem. Commun., 2011, 47, 8304–8306. and M. Schro 110 Q. Lin, T. Wu, S.-T. Zheng, X. Bu and P. Feng, Chem. Commun., 2011, 47, 11852–11854. 111 Y. Zou, C. Yu, Y. Li and M. S. Lah, CrystEngComm, 2012, 14, 7174–7177. 112 W. Wei, Z. Xia, Q. Wei, G. Xie, S. Chen, C. Qiao, G. Zhang and C. Zhou, Microporous Mesoporous Mater., 2013, 165, 20–26. 113 S. Xiong, S. Li, S. Wang and Z. Wang, CrystEngComm, 2011, 13, 7236–7245. 114 J. Y. Lee, J. M. Roberts, O. K. Farha, A. A. Sarjeant, K. A. Scheidt and J. T. Hupp, Inorg. Chem., 2009, 48, 9971–9973. 115 S. Matsunaga, S. Kato, N. Endo and W. Mori, Chem. Lett., 2013, 42, 298–300. 116 L. Meng, Q. Cheng, C. Kim, W.-Y. Gao, L. Wojtas, Y.-S. Chen, M. J. Zaworotko, X. P. Zhang and S. Ma, Angew. Chem., Int. Ed., 2012, 51, 10082–10085. 117 A. J. Cairns, J. A. Perman, L. Wojtas, V. C. Kravtsov, M. H. Alkordi, M. Eddaoudi and M. J. Zaworotko, J. Am. Chem. Soc., 2008, 130, 1560–1561. 118 X.-S. Wang, M. Chrzanowski, C. Kim, W.-Y. Gao, L. Wojtas, Y.-S. Chen, X. P. Zhang and S. Ma, Chem. Commun., 2012, 48, 7173–7175. 119 E.-Y. Choi, C. A. Wray, C. Hu and W. Choe, CrystEngComm, 2009, 11, 553–555. 120 D. Dang, P. Wu, C. He, Z. Xie and C. Duan, J. Am. Chem. Soc., 2010, 132, 14321–14323. 121 Y. Peng, T. Gong and Y. Cui, Chem. Commun., 2013, 49, 8253–8255. 122 S. Regati, Y. He, M. Thimmaiah, P. Li, S. Xiang, B. Chen and J. C.-G. Zhao, Chem. Commun., 2013, 49, 9836–9838. 123 J. M. Roberts, B. M. Fini, A. A. Sarjeant, O. K. Farha, J. T. Hupp and K. A. Scheidt, J. Am. Chem. Soc., 2012, 134, 3334–3337. 124 L. Sun, Y. Li, Z. Liang, J. Yu and R. Xu, Dalton Trans., 2012, 41, 12790–12796. 125 L. Han, L. Qin, L. Xu, Y. Zhou, J. Sun and X. Zou, Chem. Commun., 2013, 49, 406–408. 126 S. Hong, M. Oh, M. Park, J. W. Yoon, J.-S. Chang and M. S. Lah, Chem. Commun., 2009, 5397–5399. 127 X. Song, S. Jeong, D. Kim and M. S. Lah, CrystEngComm, 2012, 14, 5753–5756. 128 Y. Yan, X. Lin, S. Yang, A. J. Blake, A. Dailly, N. R. ¨der, Chem. Commun., Champness, P. Hubberstey and M. Schro 2009, 1025–1027.


View Article Online


Review Article

129 Y. Yan, I. Telepeni, S. Yang, X. Lin, W. Kockelmann, A. Dailly, A. J. Blake, W. Lewis, G. S. Walker, D. R. Allan, ¨der, J. Am. S. A. Barnett, N. R. Champness and M. Schro Chem. Soc., 2010, 132, 4092–4094. 130 V. K. Peterson, Y. Liu, C. M. Brown and C. J. Kepert, J. Am. Chem. Soc., 2006, 128, 15578–15579. 131 Y. Yan, S. Yang, A. J. Blake, W. Lewis, E. Poirier, S. A. ¨der, Chem. Commun., Barnett, N. R. Champness and M. Schro 2011, 47, 9995–9997. 132 D. Yuan, D. Zhao and H.-C. Zhou, Inorg. Chem., 2011, 50, 10528–10530. ¨ . Yazaydın, I. Eryazici, C. D. Malliakas, 133 O. K. Farha, A. O B. G. Hauser, M. G. Kanatzidis, S. T. Nguyen, R. Q. Snurr and J. T. Hupp, Nat. Chem., 2010, 2, 944–948. 134 D. Yuan, D. Zhao, D. Sun and H.-C. Zhou, Angew. Chem., Int. Ed., 2010, 49, 5357–5361. 135 Y. Yan, A. J. Blake, W. Lewis, S. A. Barnett, A. Dailly, ¨der, Chem. – Eur. J., 2011, N. R. Champness and M. Schro 17, 11162–11170. 136 D. Zhao, D. Yuan, D. Sun and H.-C. Zhou, J. Am. Chem. Soc., 2009, 131, 9186–9188. 137 O. K. Farha, C. E. Wilmer, I. Eryazici, B. G. Hauser, P. A. Parilla, K. O’Neill, A. A. Sarjeant, S. T. Nguyen, R. Q. Snurr and J. T. Hupp, J. Am. Chem. Soc., 2012, 134, 9860–9863. 138 Y. Peng, G. Srinivas, C. E. Wilmer, R. Q. Snurr, J. T. Hupp, T. Yildirim and O. K. Farha, Chem. Commun., 2013, 49, 2992–2994. 139 O. K. Farha, I. Eryazici, N. C. Jeong, B. G. Hauser, C. E. Wilmer, A. A. Sarjeant, R. Q. Snurr, S. T. Nguyen, ¨ . Yazaydın and J. T. Hupp, J. Am. Chem. Soc., 2012, 134, A. O 15016–15021. 140 B. Zheng, J. Bai, J. Duan, L. Wojtas and M. J. Zaworotko, J. Am. Chem. Soc., 2011, 133, 748–751. 141 P. L. Llewellyn, S. Bourrelly, C. Serre, A. Vimont, M. Daturi, L. Hamon, G. D. Weireld, J.-S. Chang, D.-Y. Hong, ´rey, Langmuir, 2008, Y. K. Hwang, S. H. Jhung and G. Fe 24, 7245–7250. 142 B. Zheng, Z. Yang, J. Bai, Y. Li and S. Li, Chem. Commun., 2012, 48, 7025–7027. 143 B. Li, Z. Zhang, Y. Li, K. Yao, Y. Zhu, Z. Deng, F. Yang, X. Zhou, G. Li, H. Wu, N. Nijem, Y. J. Chabal, Z. Lai, Y. Han, Z. Shi, S. Feng and J. Li, Angew. Chem., Int. Ed., 2012, 51, 1412–1415. 144 R. Luebke, J. F. Eubank, A. J. Cairns, Y. Belmabkhout, L. Wojtasb and M. Eddaoudi, Chem. Commun., 2012, 48, 1455–1457. 145 X.-J. Wang, P.-Z. Li, Y. Chen, Q. Zhang, H. Zhang, X. X. Chan, R. Ganguly, Y. Li, J. Jiang and Y. Zhao, Sci. Rep., 2013, 3, 1149. 146 C. E. Wilmer, O. K. Farha, T. Yildirim, I. Eryazici, V. Krungleviciute, A. A. Sarjeant, R. Q. Snurr and J. T. Hupp, Energy Environ. Sci., 2013, 6, 1158–1163. 147 Y. Yan, M. Suyetin, E. Bichoutskaia, A. J. Blake, D. R. Allan, ¨der, Chem. Sci., 2013, 4, S. A. Barnett and M. Schro 1731–1736.


Chem Soc Rev

148 X. Zhao, D. Sun, S. Yuan, S. Feng, R. Cao, D. Yuan, S. Wang, J. Dou and D. Sun, Inorg. Chem., 2012, 51, 10350–10355. 149 Z. Guo, H. Wu, G. Srinivas, Y. Zhou, S. Xiang, Z. Chen, Y. Yang, W. Zhou, M. O’Keeffe and B. Chen, Angew. Chem., Int. Ed., 2011, 50, 3178–3181. 150 Y. Zou, M. Park, S. Hong and M. S. Lah, Chem. Commun., 2008, 2340–2342. 151 K. Tang, R. Yun, Z. Lu, L. Du, M. Zhang, Q. Wang and H. Liu, Cryst. Growth Des., 2013, 13, 1382–1385. ´rey, 152 T. Devic, C. Serre, N. Audebrand, J. Marrot and G. Fe J. Am. Chem. Soc., 2005, 127, 12788–12789. 153 Y. He, H. Furukawa, C. Wu, M. O’Keeffe and B. Chen, CrystEngComm, 2013, 15, 9328–9331. 154 D.-X. Xue, A. J. Cairns, Y. Belmabkhout, L. Wojtas, Y. Liu, M. H. Alkordi and M. Eddaoudi, J. Am. Chem. Soc., 2013, 135, 7660–7667. 155 J. Luo, H. Xu, Y. Liu, Y. Zhao, L. L. Daemen, C. Brown, T. V. Timofeeva, S. Ma and H.-C. Zhou, J. Am. Chem. Soc., 2008, 130, 9626–9627. 156 D. Ma, B. Li, X. Zhou, Q. Zhou, K. Liu, G. Zeng, G. Li, Z. Shi and S. Feng, Chem. Commun., 2013, 49, 8964–8966. 157 Z. Chen, S. Xiang, T. Liao, Y. Yang, Y.-S. Chen, Y. Zhou, D. Zhao and B. Chen, Cryst. Growth Des., 2010, 10, 2775–2779. 158 X. Zhao, X. Wang, S. Wang, J. Dou, P. Cui, Z. Chen, D. Sun, X. Wang and D. Sun, Cryst. Growth Des., 2012, 12, 2736–2739. 159 L. Ma, D. J. Mihalcik and W. Lin, J. Am. Chem. Soc., 2009, 131, 4610–4612. 160 D. J. Mihalcik, T. Zhang, L. Ma and W. Lin, Inorg. Chem., 2012, 51, 2503–2508. 161 C. Tan, S. Yang, N. R. Champness, X. Lin, A. J. Blake, ¨der, Chem. Commun., 2011, 47, W. Lewis and M. Schro 4487–4489. 162 Z. Wei, W. Lu, H.-L. Jiang and H.-C. Zhou, Inorg. Chem., 2013, 52, 1164–1166. 163 Y.-S. Xue, F.-Y. Jin, L. Zhou, M.-P. Liu, Y. Xu, H.-B. Du, M. Fang and X.-Z. You, Cryst. Growth Des., 2012, 12, 6158–6164. 164 Y. He, Z. Zhang, S. Xiang, H. Wu, F. R. Fronczek, W. Zhou, R. Krishna, M. O’Keeffe and B. Chen, Chem. – Eur. J., 2012, 18, 1901–1904. 165 Y. He, Z. Zhang, S. Xiang, F. R. Fronczek, R. Krishna and B. Chen, Chem. – Eur. J., 2012, 18, 613–619. 166 S. C. Reyes, J. G. Santiesteban, Z. Ni, C. S. Paur, P. Kortunov, J. Zengel and H. W. Deckman, US Pat., US2009/0216059A0216051, 2009. 167 W. Zhuang, D. Yuan, D. Liu, C. Zhong, J.-R. Li and H.-C. Zhou, Chem. Mater., 2012, 24, 18–25. 168 Y.-S. Xue, Y. He, S.-B. Ren, Y. Yue, L. Zhou, Y.-Z. Li, H.-B. Du, X.-Z. You and B. Chen, J. Mater. Chem., 2012, 22, 10195–10199. 169 J. F. Eubank, H. Mouttaki, A. J. Cairns, Y. Belmabkhout, L. Wojtas, R. Luebke, M. Alkordi and M. Eddaoudi, J. Am. Chem. Soc., 2011, 133, 14204–14207. 170 Y.-S. Xue, Y. He, L. Zhou, F.-J. Chen, Y. Xu, H.-B. Du, X.-Z. You and B. Chen, J. Mater. Chem. A, 2013, 1, 4525–4530.

Chem. Soc. Rev., 2014, 43, 5618--5656 | 5655

View Article Online


Chem Soc Rev

171 Z.-J. Lin, Y.-B. Huang, T.-F. Liu, X.-Y. Li and R. Cao, Inorg. Chem., 2013, 52, 3127–3132. ¨ and R. Cao, 172 Z.-J. Lin, T.-F. Liu, Y.-B. Huang, J. Lu Chem. – Eur. J., 2012, 18, 7896–7902. 173 X.-S. Wang, M. Chrzanowski, W.-Y. Gao, L. Wojtas, Y.-S. Chen, M. J. Zaworotko and S. Ma, Chem. Sci., 2012, 3, 2823–2827. 174 X.-S. Wang, M. Chrzanowski, L. Wojtas, Y.-S. Chen and S. Ma, Chem. – Eur. J., 2013, 19, 3297–3301. 175 X.-L. Yang, M.-H. Xie, C. Zou, Y. He, B. Chen, M. O’Keeffe and C.-D. Wu, J. Am. Chem. Soc., 2012, 134, 10638–10645. 176 X.-L. Yang, C. Zou, Y. He, M. Zhao, B. Chen, S. Xiang, M. O’Keeffe and C.-D. Wu, Chem. – Eur. J., 2014, 20, 1447–1452. 177 Z. Zhang, Y. Ji, L. Wojtas, W.-y. Gao, S. Ma, M. J. Zaworotko and J. C. Antilla, Chem. Commun., 2013, 49, 7693–7695. 178 M. Li, D. Li, M. O’Keeffe and O. M. Yaghi, Chem. Rev., 2014, 114, 1343–1370. 179 O. Delgado-Friedrichs and M. O’Keeffe, J. Solid State Chem., 2005, 178, 2480–2485. 180 O. Delgado-Friedrichs, M. O’Keeffe and O. M. Yaghi, Phys. Chem. Chem. Phys., 2007, 9, 1035–1043. 181 O. Delgado-Friedrichs and M. O’Keeffe, Acta Crystallogr., 2007, A63, 344–347. 182 G.-Q. Kong, Z.-D. Han, Y. He, S. Ou, W. Zhou, T. Yildirim, R. Krishna, C. Zou, B. Chen and C.-D. Wu, Chem. – Eur. J., 2013, 19, 14886–14894. 183 J. F. Eubank, F. Nouar, R. Luebke, A. J. Cairns, L. Wojtas, M. Alkordi, T. Bousquet, M. R. Hight, J. Eckert, J. P. Embs, P. A. Georgiev and M. Eddaoudi, Angew. Chem., Int. Ed., 2012, 51, 10099–10103.

5656 | Chem. Soc. Rev., 2014, 43, 5618--5656

Review Article

184 W. Lu, D. Yuan, T. A. Makal, J.-R. Li and H.-C. Zhou, Angew. Chem., Int. Ed., 2012, 51, 1580–1584. 185 W. Lu, D. Yuan, T. A. Makal, Z. Wei, J.-R. Li and H.-C. Zhou, Dalton Trans., 2013, 42, 1708–1714. 186 J.-R. Li, D. J. Timmons and H.-C. Zhou, J. Am. Chem. Soc., 2009, 131, 6368–6369. 187 Y. He, R. Krishna and B. Chen, Energy Environ. Sci., 2012, 5, 9107–9120. 188 X. Duan, J. Cai, J. Yu, C. Wu, Y. Cui, Y. Yang and G. Qian, Microporous Mesoporous Mater., 2013, 181, 99–104. 189 D. Zhao, D. Yuan, A. Yakovenko and H.-C. Zhou, Chem. Commun., 2010, 46, 4196–4198. 190 Y. Peng, G. Srinivas, C. E. Wilmer, I. Eryazici, R. Q. Snurr, J. T. Hupp, T. Yildirim and O. K. Farha, Chem. Commun., 2013, 49, 2992–2994. 191 L. Li, S. Tang, X. Lv, M. Jiang, C. Wang and X. Zhao, New J. Chem., 2013, 37, 3662–3670. 192 S. Ma, J. M. Simmons, D. Sun, D. Yuan and H.-C. Zhou, Inorg. Chem., 2009, 48, 5263–5268. 193 T. A. Makal, X. Wang and H.-C. Zhou, Cryst. Growth Des., 2013, 13, 4760–4768. 194 B. Zheng, Z. Liang, G. Li, Q. Huo and Y. Liu, Cryst. Growth Des., 2010, 10, 3405–3409. 195 S. Matsunaga, N. Endo and W. Mori, Eur. J. Inorg. Chem., 2012, 4885–4897. 196 M. Xue, G. Zhu, Y. Li, X. Zhao, Z. Jin, E. Kang and S. Qiu, Cryst. Growth Des., 2008, 8, 2478–2483. 197 Y. He, Z. Guo, S. Xiang, Z. Zhang, W. Zhou, F. R. Fronczek, S. Parkin, S. T. Hyde, M. O’Keeffe and B. Chen, Inorg. Chem., 2013, 52, 11580–11584.


Multifunctional metal-organic frameworks: from academia to industrial applications.

Multifunctional Metal-Organic Frameworks for Photocatalysis.

Ammonia detection by using flexible Lewis acidic sites in luminescent porous frameworks constructed from a bipyridinium derivative.

Metal-organic frameworks constructed from d-camphor acid: bifunctional properties related to luminescence sensing and liquid-phase separation.

Halogen-bridged metal-organic frameworks constructed from bipyridinium-based ligand: structures, photochromism and non-destructive readout luminescence switching.

Multifunctional Supramolecular Hybrid Materials Constructed from Hierarchical Self-Ordering of In Situ Generated Metal-Organic Framework (MOF) Nanoparticles.

A Series of Lanthanide Metal-Organic Frameworks with Interesting Adjustable Photoluminescence Constructed by Helical Chains.

A novel anti-TNF scFv constructed with human antibody frameworks and antagonistic peptides.

Two novel metal borates with three-dimensional open-framework layers constructed from [M2B8O20(OH)2] (M = Al, Ga) cluster units.

Metal-organic frameworks: 3D frameworks from 3D printers.

Core-shell palladium nanoparticle@metal-organic frameworks as multifunctional catalysts for cascade reactions.

Multifunctional, defect-engineered metal-organic frameworks with ruthenium centers: sorption and catalytic properties.

A structure-directing method to prepare semiconductive zeolitic cluster-organic frameworks with Cu3I4 building units.

Construction of porous cationic frameworks by crosslinking polyhedral oligomeric silsesquioxane units with N-heterocyclic linkers.

Previously unknown class of metalorganic compounds revealed in meteorites.

Homochiral metal-organic frameworks with enantiopure proline units for the catalytic synthesis of β-lactams.

A Homochiral Multifunctional Metal-Organic Framework with Rod-Shaped Secondary Building Units.

3-D silver(I)-lanthanide(III) heterometallic-organic frameworks constructed from 2,2'-bipyridine-3,3'-dicarboxylic acid: synthesis, structure, photoluminescence, and their remarkable thermostability.

Synthesis, crystal structure, photoluminescence property and photoelectronic behavior of two uranyl-organic frameworks constructed from 1, 2, 4, 5-benzenetetracarboxylic acid as ligand.

Assembly and photocatalysis of two novel 3D Anderson-type polyoxometalate-based metal-organic frameworks constructed from isomeric bis(pyridylformyl)piperazine ligands.

Syntheses, crystal structures and UV-visible absorption properties of five metal-organic frameworks constructed from terphenyl-2,5,2',5'-tetracarboxylic acid and bis(imidazole) bridging ligands.

A retreat from SI units.

Artificial mobile DNA element constructed from the EcoRI endonuclease gene.

Performance and behaviour of planted and unplanted units of a horizontal subsurface flow constructed wetland system treating municipal effluent from a UASB reactor.