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.