Ether chain-modified Alkanolguanidine for CO2 capture and subsequent conversion

Abstract

Capturing CO2 and converting it into valuable chemicals has attracted considerable attention in recent years. Herein, a kind of ether chain-modified alkanolguanidines (ECMAs) was designed and synthesized as a dual functional reagent for carbon dioxide capture and conversion. Due to the presence of basic sites and CO2-philic ether chains, these ECMAs demonstrated almost equimolar CO2 capture at room temperature and atmospheric pressure through the synergy of physical and chemical absorption. Even for diluted CO2 (15 % CO2), 0.7 mol CO2 per mole capture reagent can still be achieved, showing their potential application in post-combustion capture. The synthesized ECMAs can also serve as catalyst in the cycloaddition reaction of CO2 with various epoxides, affording 75–99 % yield of corresponding cyclic carbonates under 3 MPa CO2 with tetrabutylammonium iodide (TBAI) as co-catalyst. Moreover, these ECMAs can be applied to the integrated CO2 capture and conversion, in which the ECMAs can react with CO2, forming the alkyl carbonate zwitterion as active CO2 species in the capture step. And in the subsequent cycloaddition reaction with propylene oxide, 52 % yield of propylene carbonate was obtained.