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Photo-induced reduction of CO2 using a magnetically separable Ru-CoPc@TiO2@SiO2@Fe3O4 catalyst under visible light irradiation† Pawan Kumar,a R. K. Chauhan,b Bir Saina and Suman L. Jain*a An efficient photo-induced reduction of CO2 using magnetically separable Ru-CoPc@TiO2@SiO2@Fe3O4 as a heterogeneous catalyst in which CoPc and Ru(bpy)2phene complexes were attached to a solid

Received 14th August 2014, Accepted 19th January 2015 DOI: 10.1039/c4dt02461c www.rsc.org/dalton

support via covalent attachment under visible light is described. The as-synthesized catalyst was characterized by a series of techniques including FTIR, UV-Vis, XRD, SEM, TEM, etc. and subsequently tested for the photocatalytic reduction of carbon dioxide using triethylamine as a sacrificial donor and water as a reaction medium. The developed photocatalyst exhibited a significantly higher catalytic activity to give a methanol yield of 2570.78 μmol per g cat after 48 h.

Photocatalytic reduction of CO2 to valuable chemicals such as methanol offers a promising way for clean, low cost and environmentally friendly production of fuels using solar energy.1 Over the past few decades, enormous efforts have been devoted to the research of TiO2 materials, which have been established as promising photocatalysts due to their low cost, low toxicity and versatility in terms of wide spread applications in various fields ranging from photovoltaics and photocatalysis to photo-/electrochromics and sensors.2,3 In spite of these virtues, TiO2 has some major drawbacks including absorption of only a small fraction ( 400 nm). The whole spectrum of LED light was used for illumination purpose. The intensity of the light at the middle of vessel was found to be 78 W m−2 as determined using an intensity meter. The vessel was charged initially with water (40 mL) and triethylamine (10 mL) and then the solution was degassed by continuous purging of nitrogen for 15 min. Then CO2 was bubbled through the solution for at least 30 min to saturate the solution. As synthesized photocatalyst 6 (100 mg) was added to the above solution and the vessel was closed tightly during the reaction and stirred vigorously to prevent the sedimentation of the catalyst. Samples were collected after every 2 h intervals with the help of a long needle and the catalyst was removed using a syringe filter (2 nm PTFE, 13 mm diameter). Quantitative determination was done by using gas chromatography FID (Varian CP-3800, having 30 m long Stabilwax® w/Integra-Guard® column) at flow rate 0.5 mL min−1, injector temp., 250 °C, and FID detector temp., 275 °C. A calibration curve was prepared for quantification and confirmation of linear response of the GC-FID system, Fig. S2.† Blank reactions were conducted to ensure that methanol production was due to the photo-reduction of CO2, and to eliminate surrounding interference. One blank reaction was carried out under visible light without the catalyst, and another was performed in the dark in the presence of catalyst under identical experimental conditions. An additional blank test was vis-illuminated with the catalyst filling N2 rather than CO2. No product was detected in the above three blank tests.

Acknowledgements We kindly acknowledge Director, CSIR-IIP for his kind permission to publish these results. PK is thankful to CSIR, New

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Photo-induced reduction of CO2 using a magnetically separable Ru-CoPc@TiO2@SiO2@Fe3O4 catalyst under visible light irradiation.

An efficient photo-induced reduction of CO2 using magnetically separable Ru-CoPc@TiO2@SiO2@Fe3O4 as a heterogeneous catalyst in which CoPc and Ru(bpy)...
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