Recent advances in the coupling of CO2 and epoxides into cyclic carbonates under halogen-free condition

Abstract

The chemical transformation of CO2 and epoxides into cyclic carbonates has been receiving much attention and is one of the successful examples for CO2 utilization as carbon resource. Many catalysts containing halide anions have been explored and exhibit excellent catalytic activity. However, halogen salt is generally toxic and corrosive to reactors. From a green chemistry perspective, it is more attractive to develop a halogen-free catalyst with excellent performance. Herein, a review of recent research progress of halogen-free catalysts in the cycloaddition of CO2 and epoxide is presented. According to previous experimental and theoretical works, two possible strategies for achieving the halogen-free process were summarized. The relationship between catalytic activity and catalyst structure, the mechanism of CO2 activation should be both studied deeply combined with experimental results and DFT calculation, which can guide the design of new catalysts and realize halogen-free process under mild reaction conditions.