CO2 Capture by Imidazolate-Based Ionic Liquids: Effect of Functionalized Cation and Dication

Given the fact that the basicity of imidazolate was higher than that of acetate, imidazolate-based ionic liquids (ILs) were developed to be studied. By combining six different cations, including traditional cation, functionalized cation, and dication, together with imidazolate, a series of ILs were prepared and found to be effective for CO 2 capture. The mechanism of the studied ILs was proposed as the formation of the carboxylation reactions on C2 position of the imidazolium rings. A strong interaction between the newly formed carboxylate portion of the zwitterion and the C2–H proton of another cation was also formed, leading to a 0.5 molar ratios of CO 2 to IL. In addition, the CO 2 absorption capacity of dicationic IL was 1.0 molar ratio, twice that of the monocationic analogue. Significantly, an improvement on absorption result was exhibited by the amino-functionalized IL, but similar performance was not observed in the hydroxyl-functionalized one. The effects of operating pressure and temperature on CO 2 absorption were also discussed.