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.