Mechanisms of CO<sub>2</sub> Absorption in Amino Acid-Based Deep Eutectic Solvents: Insights from Molecular Dynamics and DFT Calculations
Hung-Yi Chi, Heng‐Kwong Tsao, Yu‐Jane Sheng
Abstract
High Resolution Image Download MS PowerPoint Slide This study explores the mechanisms of CO 2 absorption in two amino acid-containing deep eutectic solvents (DESs) through molecular dynamics (MD) simulations and density functional theory (DFT) calculations. The MD simulations, which focus mainly on physical absorption, reveal that alanine-based DES (Ala DES) exhibits higher CO 2 solubility than l -arginine-based DES ( l -arg DES), attributed to stronger physical absorption. Furthermore, the hydrogen bond donor paired with the amino acids is identified as a critical factor for enhancing physical absorption efficiency. DFT calculations, which account for chemical absorption, investigate two reaction pathways: single-molecule reactions involving intramolecular proton transfer and two-molecule reactions involving intermolecular proton exchange. While Ala DES does not exhibit spontaneous chemical absorption, l -arg DES demonstrates such reactions, leading to the formation of carbamic acid or carbamate (Δ G < 0), indicative of CO 2 capture through chemical interactions. Consequently, Ala DES primarily relies on physical absorption, whereas l -arg DES utilizes multiple reactive sites for chemical absorption. These results are consistent with experimental findings, which show that l -arg DES achieves higher CO 2 solubility under atmospheric conditions. Overall, our study highlights the interplay between DES components and reactivity in enhancing CO 2 capture efficiency.