Deciphering the role of non-covalent interactions in CO₂ Capture: A DFT and COSMO-RS study of amino acid-based ionic...

A computational investigation into the interactions between amino acid based ionic liquids (AAILs) and carbon dioxide has provided valued discernments into the molecular mechanisms leading to CO₂ capture. Using DFT and COSMO-RS simulations, the adsorption affinity of three AAILs based on lysinate, Arginate and Glycinate based amino acids anions tehthered with with counter cation 1-Methyl-3-(3-sulfopropyl)-imidazolium [1MeimPS]+ with CO₂ is explored. The interaction of nCO₂ (n = 1) with lysine based AAIL-1CO₂ showed superior adsorption energy of -2.820 kcal/mol, whereas arginine based AAIL-1CO₂ showed least adsorption energy of -1.966 kcal/mol. Similarly, for nCO₂ (n = 2), the lysine based AAIL 2CO₂ showed nearly double the adsorption energy of -4.6831 kcal/mol compared to lysine based AAIL 1CO₂. On contrary, arginine based AAIL-2CO₂ has even less adsorption energy of -1.901 kcal/mol compared to [1MeimPS][Arg]-1CO_2. However, the introduction of second CO₂ molecule reduces the bond distances for AAILs--1CO₂, further strengthened and fine-tuned the CO₂ adsorption. Also, CO₂ solubility of AAILs is investigated ranging from 288.15 to 353.15 K at 5.0-45 bar revealed that temperature has inverse relationship with solubility, illustrating that the combination of [Gly]^- and [Lys]^- anions with cation [1MeimPS]⁺ is effective for efficient CO₂ capture and separation. Furthermore, Natural Bond Orbital (NBO) analyis showed the significant charge trasfer in lysine based AAIL nCO₂ compared to other ILs. Also, anions have the appreciable chances of strong dispersion interactions with CO₂ as revealed by Quantum Atoms in Molecules (QTAIM), and Interaction Region Indicator (IRI) plots. Among, ILs bearing multiple amine groups, lysine based AAIL displayed favorable activity coefficient (γ^∞) values suggesting efficient and stable interactions with CO₂ as evidenced by Adsorption Energy E_ads, QTAIM topologies and IRI isosurfaces. Understanding multiple interactions between ILs and nCO₂ paved the ways to design ILs for CO₂ adsorption and separation for environmental challenges.