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Carbon Dioxide Absorption in Amino Acid Ionic Liquids and Salt Solutions


The efficient capture and storage of post-combustion carbon dioxide has attracted immense interest in the search for materials in the area of carbon capture and storage/sequestration technology. Amino Acid Ionic Liquids and salt solutions are possible replacements as CO2 absorbents due to better recyclability and reusability, in contrast to traditionally used amines. Compared to other amino acids, Lysine, in its anionic form absorbs CO2 in a 2:1 molar ratio, due to the presence of two amine functional groups and an adjacent carboxylate group. The objective of this research program is to understand the mechanism, structure and dynamics of CO¬2 absorption in Ionic Liquids and salt solutions with the lysinate anion. The amount of CO2 absorption calculated from MD simulations agrees well with experimental data. The simulations provide insights on the timescales associated with various processes of CO2 absorption. The simulations are used to extract the mobility of CO2/absorbent molecules at varying thermodynamic conditions (temperature, pressure). The quantum chemistry calculations provide a distribution of products formed on absorption of CO2 on various sites of the lysinate anion. The role of water in aqueous solutions of Lysinate salts, e.g. potassium lysinate (promising CO2 absorbent) is now explored using quantum chemistry calculations and MD simulations. The outcomes from the work can serve as a benchmark for understanding CO2 absorption in other salts/ionic liquids with similar cations and/or other amino acid anions. The findings can motivate experimental investigations to screen, synthesize and characterize efficient ILs for CO2 capture and also optimize the functionality of anions to enhance absorption.