Exploring the General Characteristics of Amino-Acid-Functionalized Ionic Liquids through Experimental and Quantum Chemical Calculations

Amino-acid-functionalized ionic liquids (AAILs) show significant potential for energy-efficient post-combustion CO2 capture. In this work, the interaction energy calculation was performed with the Gaussian 09 package, and the activation barriers and energy change calculation were performed with the Material Studio 7.0 package. The experimental and quantum chemical calculation results showed that both the CO2 absorption capacity and the viscosity of AAILs were negatively correlated to their interaction energy. The results of 13C nuclear magnetic resonance analysis and activation barriers indicated that, under the same conditions, the effect of the AAIL cation on the regeneration ability was more significant than that of the anion. In our previous work, CO2 absorption into AAIL solution was proven to be divided into two periods. In the first period, carbamate was produced after the CO2 absorption reaction, and in the second period, the production was carbonate. Research on thermodynamic properties in this work made the mechanism for CO2 capture into AAILs more clear. The activation barrier, energy change, and enthalpy change during the two periods revealed that the AAIL–CO2 absorption reaction should be a neutralizing and exothermic reaction in the first period and a hydrolysis and endothermic reaction in the second period.