N-Heterocyclic carbene functionalized MCM-41 as an efficient catalyst for chemical fixation of carbon dioxide

Abstract

N-Heterocyclic carbene (NHC) functionalized MCM-41 was synthesized by reacting 1,3-bis-(4-allyl-2,6-diisopropylphenyl) imidazolium chloride with MCM-41 using 3-mercaptopropyltrimethoxysilane as silane coupling agent, and its CO2 adduct (designated as MCM-41-IPr-CO2) was further synthesized by the reaction with CO2. In situdiffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to investigate the reversible CO2 capture-release ability of MCM-41-NHC. MCM-41-IPr-CO2 adduct proved to be an efficient heterogeneous catalyst for the cycloaddition of CO2 to epoxides or aziridines with excellent regioselectivity under mild conditions. Moreover, the catalyst could be recovered easily through a simple filtration process and reused multiple times without obvious loss in activity, owing to CO2 as protective group for effectively stabilizing the NHC anchored on MCM-41.