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Mechanism of Formic Acid Disproportionation Catalyzed by an Iridium Complex Immobilized on Bipyridine‐Periodic Mesoporous Organosilica: A Case Study Based on Kinetics Analysis
Author(s) -
Yamaguchi Sho,
Hashimoto Shunsuke
Publication year - 2020
Publication title -
asian journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.846
H-Index - 44
eISSN - 2193-5815
pISSN - 2193-5807
DOI - 10.1002/ajoc.201900692
Subject(s) - chemistry , disproportionation , catalysis , selectivity , dehydrogenation , kinetics , formic acid , methanol , iridium , bipyridine , mesoporous material , heterogeneous catalysis , inorganic chemistry , photochemistry , organic chemistry , physics , quantum mechanics , crystal structure
This work investigated the kinetics of formic acid (FA) disproportionation using an Ir complex immobilized on bipyridine‐periodic mesoporous organosilica (BPy‐PMO). The selectivity for methanol (MeOH) is increased using this catalyst compared to conventional homogeneous Ir complexes. This enhanced selectivity is attributed to the retention of H 2 and CO 2 generated by the competing FA dehydrogenation in PMO mesochannels having a high aspect ratio. However, no direct evidence for this process was previously obtained. The present work clarified the unique catalysis mechanism associated with a PMO catalyst exhibiting higher MeOH selectivity based on a hypothesis that the generation of MeOH via FA hydrogenation is promoted by the confinement of H 2 in the PMO pores. The results obtained from the present kinetics study and data regarding H 2 diffusion in the PMO pores strongly support this hypothesis.