Amino acid ionic liquids as efficient catalysts for CO₂ capture: A combined static and dynamic approach

Amino acid ionic liquids (AAILs) have gained significant attention as green solvents that are biocompatible, biodegradable, and useful in various applications, including catalysts, absorbents, and solvents. This study investigates the detailed interactions of three amino acid anions (glycine [Gly]^-, histidine [His]^-, and arginine [Arg]^-) with the cation 1-methoxylbutyl-3-methylimidazolium [MOBMIM]⁺ and their role in CO₂ absorption using quantum mechanical calculations and molecular dynamics (MD) simulations. The Density Functional Theory (DFT) calculations elucidate the reaction mechanisms underlying CO₂ absorption and cycloaddition, and facilitate a comparative analysis of the impact of different amino acids on these reactions, and the synergies between them. Notably, arginine displays superior CO₂ absorption capacity in comparison to glycine and histidine. Additionally, the cycloaddition reaction with CO₂ exhibits a lower energy barrier when arginine is involved. Insights from the MD simulations highlight the higher level of electrostatic interaction between [MOBMIM]⁺[Arg]^- and CO₂, relative to the other studied molecules. Moreover, the Lennard Jones interaction emerges as the dominant type of interaction in these systems. The diffusion coefficient for CO₂ was highest when interacting with [MOBMIM]⁺[Gly]^-, followed by [MOBMIM]⁺[Arg]^-. Consequently, both MD and DFT investigations converge to suggest that [MOBMIM]⁺[Arg]^- followed by [MOBMIM]⁺[Gly]^- may serve as advantageous choices for CO₂ fixation and cycloaddition. The findings from this study underscore the considerable potential of the investigated AAILs as materials conducive to CO₂ capture and utilization, thus paving the way for the integration of CO₂ capture into valuable chemical products.