The dynamic behavior and intrinsic mechanism of CO 2 absorption by amino acid ionic liquids.

Reducing carbon dioxide emissions is one of the possible solutions to prevent global climate change, which is urgently needed for the sustainable development of our society. In this work, easily available, biodegradable amino acid ionic liquids (AAILs) with great potential for CO ₂ absorption in the manned closed space such as spacecraft, submarines and other manned devices are used as the basic material. Molecular dynamics simulations and ab initio calculations were performed for 12 AAILs ([P4444][X] and [P66614][X], [X] = X = [GLy] ^- , [Im] ^- , [Pro] ^- , [Suc] ^- , [Lys] ^- , [Asp] ^2- ), and the dynamic characteristics and the internal mechanism of AAILs to improve CO ₂ absorption capacity were clarified. Based on structural analysis and the analysis of interaction energy including van der Waals and electrostatic interaction energy, it was revealed that the anion of ionic liquids dominates the interaction between CO ₂ and AAILs. At the same time, the CO ₂ absorption capacity of AAILs increases in the order [Asp] ^2- < [Suc] ^- < [Lys] ^- < [Pro] ^- < [Im] ^- < [Gly] ^- . Meanwhile, the synergistic absorption of CO ₂ by multiple-sites of amino and carboxyl groups in the anion was proved by DFT calculations. These findings show that the anion of AAILs can be an effective factor to regulate the CO ₂ absorption process, which can also provide guidance for the rational and targeted molecular design of AAILs for CO ₂ capture, especially in the manned closed space.