Carboxylate-Functionalized Zeolitic Imidazolate Framework Enables Catalytic N-Formylation Using Ambient CO2

Catalytic upgrading of CO2 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 CO2 to furnish N-formyl compounds (up to 99% yield) in the presence of PhSiH3 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 CO2. The powerful adsorption capacity of the F-ZIF-90 catalyst toward CO2 is conducive to elevating CO2 concentration around the active species. Theoretical calculations show that the carboxylatemediated conversion path undergoes the transition state of hydrosilane activation with a relatively lower energy barrier (Delta G = 26.9 kcal mot(-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 CO2.