Potter, Matthew, Stewart, Daniel, Elliott, Stuart J, Sazio, Pier-John, Zhang, Liling, Luo, He Kuan, Zhang, Zhongxing, Teng, Jing Hua, Ivaldi, Chiara, Miletto, Ivana, Gianotti, Enrica, Raja, Robert and Webb, William (2018) Imidazole functionalized MIL-101(Cr), via metal coordination, as a highly active catalyst for carbon dioxide utilization. American Chemical Society National Meeting & Exposition: Nanoscience, Nanotechnology & Beyond, , Boston, United States. 19 - 23 Aug 2018.
Abstract
Metal organic frameworks (MOFs) are hugely flexible materials with a vast variety of applications. As catalysts, they show great promise owing to their highly porous nature, large surface area, thermal and chemical stability and ease of modification – metal node and linker are variable during and post synthesis. As
solids, MOFs are heterogeneous catalysts which can be more active and are more easily recycled, providing a more environmentally benign alternative to their homogenous analogues. The work presented shall display the effect of post synthetic modification (PSM) of MIL-101, a chromium based terephthalate MOF. Unmodified, MIL-101 shows moderate catalytic activity in CO utilization forming cyclic carbonates. A facile PSM technique, see Figure 1, to incorporate 1-methyl imidazole on the coordinatively unsaturated sites (CUS) of MIL-101 is shown to significantly improve the catalytic performance. Extensive characterisation (XRD, SEM, TGA, BET, and XPS), confirm the retention of the framework following
PSM, whilst FT-IR, UV-Vis and EPR affirm imidazole location on the CUS. Well dispersed, isolated sites for CO utilization are therefore created, without significant alteration of the framework properties. Cataltyic results for the reaction of butylene oxide with CO with MIL-101-Me give an 80 % yield, Figure 1, at a turnover frequency of 770 hr , which compared to the unmodified MIL-101, 30 %, is appreciably enhanced. Computational modelling provides explanation of the unprecedented activity whereby simulations show the
addition of the imidazole introduces additional CO binding sites, prompting the formation of CO -epoxide clusters which increase likelihood of reaction. Both recycle tests and post-catalysis characterisation have proven the MIL-101-Me maintains activity and structure over several cycles.
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