Carboxylate-Functionalized Zeolitic Imidazolate Framework Enables Catalytic N-Formylation Using Ambient CO2
Catalytic upgrading of CO 2 into value-added chemicals to build the excess carbon cycle is of great significance. In this work, carboxylate-functionalized zeolitic imidazolate framework (F-ZIF-90) with good crystallinity and porosity is constructed from ZIF-90 and employed as a robust heterogeneous catalyst to boost the reductive N -functionalization of various amines with CO 2 to furnish N -formyl compounds (up to 99% yield) in the presence of PhSiH 3 under an ambient environment. The imidazole carboxylate species ( COO - ) can not only activate hydrosilane and CO 2 to form the key intermediate formoxysliane but also activate amines to participate in the N -formylation reaction to obtain the target product. Moreover, it can enhance the catalyst capture and exchange ability toward ambient CO 2 . The powerful adsorption capacity of the F-ZIF-90 catalyst toward CO 2 is conducive to elevating CO 2 concentration around the active species. Theoretical calculations show that the carboxylate-mediated conversion path undergoes the transition state of hydrosilane activation with a relatively lower energy barrier (Δ G = 26.9 kcal mol –1 ). F-ZIF-90 exhibits good thermochemical stability with no obvious activity attenuation after repeated use 5 times. This strategy opens a new avenue based on ZIFs to develop heterogeneous catalysts for reductive upgrading of CO 2 .
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