Progress in Nuclear Magnetic Resonance Spectroscopy 77 (2014) 1–48

Contents lists available at ScienceDirect

Progress in Nuclear Magnetic Resonance Spectroscopy journal homepage: www.elsevier.com/locate/pnmrs

Recent NMR developments applied to organic–inorganic materials Christian Bonhomme a,⇑, Christel Gervais a, Danielle Laurencin b a Laboratoire de Chimie de la Matière Condensée de Paris, UMR CNRS 7574, Université Pierre et Marie Curie, Paris 06, Collège de France, 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France b Institut Charles Gerhardt de Montpellier, UMR5253, CNRS UM2 UM1 ENSCM, CC1701, Place Eugène Bataillon, 34095 Montpellier Cedex 05, France

Edited by J.W. Emsley and J. Feeney

a r t i c l e

i n f o

Article history: Received 17 July 2013 Accepted 17 October 2013 Available online 26 October 2013 Keywords: Solid state NMR Organic–inorganic materials Hybrid materials Interface Structure

a b s t r a c t In this contribution, the latest developments in solid state NMR are presented in the field of organic–inorganic (O/I) materials (or hybrid materials). Such materials involve mineral and organic (including polymeric and biological) components, and can exhibit complex O/I interfaces. Hybrids are currently a major topic of research in nanoscience, and solid state NMR is obviously a pertinent spectroscopic tool of investigation. Its versatility allows the detailed description of the structure and texture of such complex materials. The article is divided in two main parts: in the first one, recent NMR methodological/ instrumental developments are presented in connection with hybrid materials. In the second part, an exhaustive overview of the major classes of O/I materials and their NMR characterization is presented. Ó 2013 Elsevier B.V. All rights reserved.

Contents 1. 2.

3.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Experimental and theoretical NMR developments applied to the study of organic–inorganic materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Texture of porous materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 129/131 2.1.1. Xe NMR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 83 2.1.2. Kr, 13C, and 1H NMR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1.3. PFG NMR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1.4. MAS PFG NMR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.2. DOSY NMR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.3. Increasing NMR sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.3.1. Microcoils and MAS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.3.2. PHIP and MRI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.3.3. DNP MAS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.4. First principles calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.4.1. Metal organic frameworks and related metal organic ligand crystalline compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.4.2. Crystalline templated systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.4.3. Interfaces in disordered systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.4.4. Functionalized metallic clusters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Recent applications of solid state NMR to organic–inorganic materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 3.1. Hybrid silicas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 3.1.1. Advanced solid state NMR techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3.1.2. Encapsulation of molecules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 3.1.3. Interfaces in silica derived hybrids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

⇑ Corresponding author. E-mail address: [email protected] (C. Bonhomme). 0079-6565/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.pnmrs.2013.10.001

2

C. Bonhomme et al. / Progress in Nuclear Magnetic Resonance Spectroscopy 77 (2014) 1–48

4.

3.1.4. Bioactive silica derived hybrid materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.5. Polyhedral silsesquioxanes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.6. Ionogels and nanoparticle networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2. Hybrid materials involving an ionic solid as inorganic component . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.1. Hybrid phosphate-based materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.2. Hybrid cationic clays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.3. Hybrid anionic clays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.4. Functionalized micro/nanoparticles of metal oxides and other ionic solids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.5. Other hybrid materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3. Biomaterials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.1. Natural biomaterials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.2. Synthetic bio-inspired materials and coatings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4. Hybrid structures involving metal complexes and coordination networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.1. Simple metal complexes and clusters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.2. Coordination polymers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.3. Metal Organic Frameworks (MOFs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.4. Functionalized metal nanoparticles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Summary and outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . List of abbreviations and acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1. Introduction Organic/inorganic (O/I) materials (or hybrid materials) are now fully integrated in the field of nanosciences [1]. They are multifunctional by nature, and can be used as innovative advanced materials. They can also act as precursors to new materials with highly attractive properties in optics, electronics, membranes, functional coatings and sensors [2]. Their synthesis and characterization require a true multidisciplinary approach, involving chemistry, physics, materials science and processing, engineering, and in some cases biology. From a structural point of view, hybrids show a high degree of complexity, as they correspond to multicomponent assemblies exhibiting interfaces. These O/I interfaces are often difficult to characterize [3]. Solid state NMR is a key characterization technique, as it allows one not only to investigate the local environment of nuclei (through various NMR interactions, such as the chemical shift, d, or the quadrupolar interaction, Q), but also the longer range connectivities between nuclei (using either throughbond, indirect (or scalar) spin–spin (J), or through-space, dipolar (D) interactions). In 2009, Geppi et al. [4] reviewed some applications of NMR to the description of hybrid materials. First, they proposed a definition of an O/I material: ‘‘[it is] a material constituted by both organic and inorganic components, where the average domain sizes of either one or both components range from nano- to micrometers [. . .] both components exhibit a functional role in determining the final properties of the material’’. They then reviewed the main spectroscopic targets for hybrid components: 29Si, 1H, 13C (and some quadrupolar nuclei such as 27Al, 17O). They selected studies related to the nature of O/I interfaces, local dynamics (via cross-polarization Magic Angle Spinning (CP MAS) or 2H NMR), measurement of domain sizes [5], and conformation of the polymeric components. In terms of NMR sequences, 2D 1H–29Si(13C) CP MAS, 1 H–1H double-quantum (DQ) MAS, Nuclear Overhauser Effect Spectroscopy (NOESY), 1H–1H spin diffusion experiments and relaxation time measurements were particularly emphasized. More recently, Alonso and Marichal published a detailed tutorial review on solid state NMR applied specifically to micelle-templated mesoporous solids [6]. All the panel of the NMR interactions was used here for full spectroscopic characterization of these hybrid materials at different scales. Topics such as the formation,

19 19 19 20 20 21 22 22 23 24 24 27 28 28 29 30 32 33 33 33

the structural characterization, the surface and texture of materials, were illustrated. During the last 5 years, major instrumental/methodological NMR developments have been achieved [7,8] including: (i) ultra-high magnetic field (up to 23.5 T, m0(1H) = 1 GHz) [9]; (ii) ultra-fast magic angle spinning (up to mrot = 100 kHz) [10], (iii) extension of NMR techniques to paramagnetic samples [11,12]; (iv) new decoupling/recoupling NMR schemes, including sequences dedicated to quadrupolar nuclei [7,8,13–15]; (v) new broadband excitation schemes [16,17]; (vi) increase in NMR sensitivity by orders of magnitude, including the use of microcoils [18], para-hydrogen induced polarization (PHIP) [19] and dynamic nuclear polarization (DNP) [20]. The problem of sensitivity in NMR is indeed crucial in the case of specific processing of hybrid materials. Quoting a review article by Sanchez et al. [21]: ‘‘. . . In our opinion, techniques that can give accurate information (either ex situ and in situ) on the chemical speciation of periodically organized mesoporous films are still lacking’’. In particular, the detailed chemical speciation of hybrid mesoporous films remains highly difficult to establish. Here, the key problem is obviously related to mass-limited samples to be analyzed. For example, if we consider a unique film of porous hybrid silica with the following characteristics: surface area, S = 2 cm2; thickness = 300 nm; density, q  1.5 g cm3 (depending on the porosity), the order of magnitude of the sample mass is less than 0.1 mg. Such a mass of sample is clearly challenging for conventional solid state NMR spectroscopy. The studies of hybrid materials have clearly benefited from the experimental and methodological developments of NMR, by helping establish their structure at the atomic level as well as their texture. The aim of this review is to illustrate this by selected examples. Thus, examples of advanced NMR characterizations of hybrid materials will be given, focusing not only on hybrid phases such as those initially defined by Geppi et al. [4], but also on materials whose structure can be related to one of the components of a complex hybrid material. Indeed, we have chosen to include for example recent solid state NMR investigations of simple metal complexes bearing organic ligands and coordination polymers, because this can be useful for synthetic materials chemists, so that they know which NMR experiments can serve as a starting point for characterizing more complex hybrid phases.

C. Bonhomme et al. / Progress in Nuclear Magnetic Resonance Spectroscopy 77 (2014) 1–48

Section 2 deals with methodological NMR developments applied to the characterization of O/I materials. 129/131Xe, pulsed field gradient (PFG), MAS PFG, and diffusion ordered spectroscopy (DOSY) NMR (Sections 2.1 and 2.2) are presented as pertinent spectroscopic tools of investigation of hybrid phases. New methods leading to a major increase in sensitivity are also presented (including microcoils under MAS, PHIP and DNP – Section 2.3). A large subsection is then devoted to first principles calculations of NMR parameters (Section 2.4), following the pioneering work of Pickard and Mauri and the introduction of the GIPAW (Gauge Including Projector Augmented Wave) method [22]. Though two recent reviews on GIPAW were recently published in the literature [23,24], we emphasize here applications to hybrid materials and O/ I interfaces, considering both periodic and cluster density functional theory (DFT) approaches. Section 3 illustrates recent applications of NMR to O/I materials by focusing on four main families of compounds. Section 3.1 concerns hybrid silicas (as silica is ubiquitous as inorganic component in a large variety of O/I materials). Several classes of silica derived materials, such as bioactive silica, polyhedral silsesquioxanes (POSS), ionogels and nanoparticle networks, are reviewed. Emphasis is stressed on new developments related to very high-field ultra-fast MAS NMR. Section 3.2 deals with ionic hybrid solids, including phosphate based materials, hybrid cationic/anionic clays, and functionalized micro/nanoparticles of ionic solids and metal oxides. Section 3.3 is devoted to the detailed description of biomaterials. Natural biomaterials, such as diatoms (based on amorphous silica), bones and teeth (based on calcium phosphates) and CaCO3 based derivatives, are first described, before focusing on synthetic bioinspired materials. Finally, Section 3.4 is related to NMR applied to metal complexes, coordination polymers (involving phosphonate, carboxylate and cyanide ligands, just to name a few), metal organic frameworks (MOFs) and functionalized metal nanoparticles. 2. Experimental and theoretical NMR developments applied to the study of organic–inorganic materials In this section, we emphasize new instrumental/methodological developments related to solid state NMR applied to the characterization of O/I materials. These developments concern first the texture of hybrids and their characterization by hyperpolarized (HP) gas and PFG NMR techniques. Gradients are also an essential part of DOSY, which appears as a valuable tool of investigation for functionalized nanoparticles. During the past 5 years, impressive developments have been published on methods for improving NMR sensitivity. Among other techniques, micro-coils, PHIP and DNP will be described, as well as illustrative applications in the field of hybrid materials. 2.1. Texture of porous materials The texture of organic–inorganic materials is a fundamental characteristic that has to be taken into account for potential applications. Among various parameters, the fine description of the porosity of the materials is of paramount importance. Several physico-chemical techniques can be implemented to measure the intrinsic porosity, among which is 129Xe NMR spectroscopy. In this section, we will focus mainly on hyperpolarized (HP) 129Xe NMR, as it allows a very large increase in sensitivity. The advantage of this technique for the characterization of porous materials, whether purely inorganic or hybrid, will be demonstrated. Moreover, the transport of matter through diffusion inside the pores of the mate-

3

rials is also a crucial parameter to measure. PFG methods are particularly suited for this purpose, with or without rotation of the sample at the magic angle.

2.1.1. 129/131Xe NMR Thermally polarized xenon NMR has been used for decades for the characterization of porous materials such as zeolites, mesoporous silicas and silica glasses [25–29]. Indeed, the NMR parameters of xenon such as the isotropic chemical shift, the chemical shift anisotropy (CSA), the linewidth and the longitudinal relaxation time T1 are able to encode useful information related to the porosity and the internal surface of materials. The xenon NMR technique has been largely improved with the introduction of hyperpolarization via optical pumping methods [30–33]. In this case, spin polarization can be enhanced by four orders of magnitude when compared to that at thermal equilibrium. Continuous flow hyperpolarized 129Xe NMR has been used to characterize the unique pseudo-hexagonal form of tris(o-phenyldioxy)cyclophosphazene (TPP) [34]. This form can be considered as an empty nanoporous structure comparable to a zeolite-like architecture. Indeed, it exhibits stability at room temperature (RT) and the open channels are accessible to gases and guest molecules. It was demonstrated that the shape of the nanopores is close to a regular cylinder (whose diameter is actually slightly larger than the diameter of Xe  4.4 Å). It follows that the diffusion of Xe in the nanopores is essentially fast and uniaxial. Continuous flow HP 129 Xe allowed: (i) recording 129Xe spectra with short recycle delays – here, 200 ms. (ii) recording 129Xe spectra with acceptable signalto-noise (S/N) ratio with very low concentration of Xe (1% of Xe diluted in He). The symmetry of the electronic shell of Xe is clearly reflected in the observation of the 129Xe CSA, with a clear change of its sign when increasing the Xe % in the helium medium. At low Xe%, the CSA pattern is representative of the Xe-wall interactions, whereas the Xe–Xe interactions dominate at high Xe%. Very interestingly, these opposite effects vanish almost completely for Xe%  30%, and, as a consequence, an isotropic 129Xe spectrum (with almost no residual CSA) was observed. More recently [35], the kinetics of the exchange of Xe between the gas and the channels was described in self-assembled L-alanyl-L-valine nanotubes using continuous flow HP 129Xe, as well as 2D exchange spectroscopy (EXSY). HP 129Xe NMR was successfully applied to the characterization of silica derived mesoporous materials exhibiting amorphous walls [36]. The same approach was also applied to more organized silica walls [37]. Variable temperature (VT) experiments clearly demonstrated the existence of various well defined Xe species: free gas, adsorbed and condensed species on the silica walls. The evolution of d(129Xe) vs. temperature led to the evaluation of the adsorption DH value. From a dynamical point of view, variable temperature 2D HP 129Xe EXSY experiments demonstrated that Xe gas phase access the mesopores on the ms timescale. In a series of contributions, SBA (Santa Barbara) derived architectures were described by means of various Xe NMR techniques by Gedeon and coworkers (these particular mesoporous silica with periodic 50–300 Å pores are obtained starting from triblock copolymers). The crystallization of Al-SBA-15 amorphous walls into ZSM-5 derived materials was studied by HP 129Xe NMR [38] leading to the detailed characterization of the interconnection of the porous network. In the case of arenesulfonic functionalized SBA-15 [39], with variable organic contents, the spectra obtained at various Xe pressures and temperatures acted as pertinent fingerprints of the organic species. It became possible to characterize the homogeneity of the mesoporous porosity towards the organic covering. Most

4

C. Bonhomme et al. / Progress in Nuclear Magnetic Resonance Spectroscopy 77 (2014) 1–48

interestingly, 1H spectral editing was performed by using 1H–129Xe CP [32] and SPINOE [40,41] experiments. SBA structures exhibiting unimodal and bimodal porosities were also characterized by 129Xe NMR spectroscopy [42]. From a more general point of view, correlations between d(129Xe) and pore size of mesoporous solids were proposed by Haddad et al. [43]. In an interesting study, Liu et al. [44] demonstrated the close stacking of MCM-49 and ZSM-35 structures in co-crystallized zeolites. Indeed, very fast exchange of Xe could be monitored in co-crystals: this exchange was even faster than in the case of analogues obtained under mechanical mixing. The same approach was applied to the study of hierarchical porous structures in mesoporous modified zeolites (ZSM-5) [45]. The intrinsic sensitivity of HP 129 Xe NMR was successfully used for the detection of very low amounts of crystalline zeolites (