Molecular Simulations of CO2-Ionic Liquid Interactions in Choline Amino Acid Systems

Global warming driven by greenhouse gas emissions, particularly carbon dioxide (CO2), has become a critical environmental challenge. Carbon capture, utilization, and storage (CCUS) technologies are therefore essential for mitigating global carbon emissions. In this context, choline-based amino acid ionic liquids have attracted significant attention as eco-friendly CO2 absorbents due to their biodegradability and biocompatibility. In this study, the structural and dynamical properties of choline-based amino acid ionic liquids, [Ch][Gly] and [Ch][Ser], were systematically investigated using classical molecular dynamics simulations at 300 K. Local structural organization and intermolecular correlations were analyzed through radial distribution functions, elucidating cation-cation, anion-anion, cation-anion, and hydrogen-bonding interactions, as well as specific interactions with CO2 and water molecules. Spatial distribution function analysis revealed preferential coordination environments of CO2 and water around the ionic liquid components, highlighting their role in governing local structural arrangements. Furthermore, structure factor analysis showed the absence of a prepeak in the low-q region, indicating a homogeneous microscopic organization in both [Ch][Gly] and [Ch][Ser] IL.