An efficient absorbent of amine-based amino acid-functionalized ionic liquids for CO2 capture: High capacity and regeneration ability

• An amine-based amino acid-functionalized ionic liquid was designed for CO2 capture.
• The capacity of [APmim][Gly] was found to be 1.23 mol CO2/mol IL (4.31 mol CO2/kg IL).
• CO2 firstly reacted with [APmim][Gly] to form carbamate and followed by hydration.

An efficient and high capacity absorbent of amine-based amino acid-functionalized ionic liquid (IL) ([APmim][Gly]) was designed and prepared for CO2 capture in this work. The achieved capacity of [APmim][Gly] was 1.23 mol CO2/mol IL (4.31 mol CO2/kg IL), which was much higher than that of the most existing dual functionalized ILs due to its low molecular weight. The largest weight loss temperature of [APmim][Gly] was found to be 370 °C, at that point, the weight loss was nearly 60% of its initial weight. Besides, [APmim][Gly] also owned a high regeneration ability even after multiple regenerations. In order to clarify the reaction mechanism of CO2 absorption into [APmim][Gly] solution, 13C nuclear magnetic resonance (NMR) was carried out to analyze the species of [APmim][Gly] solution at different CO2 loadings. Different from the most reported mechanisms for CO2 capture into functionalized ILs, the reaction between [APmim][Gly] and CO2 was influenced by CO2 loadings. The reaction could divide into two stages. It was started with the reversible chemical reaction to form carbamate, and followed by the CO2 hydration reaction. At high CO2 loading, the production of carbamate was easy to be decomposed.