AUTHOR=Siami Hasan , Razmkhah Mohammad , Moosavi Fatemeh 

TITLE=Cation functional group effect on SO2 absorption in amino acid ionic liquids

JOURNAL=Frontiers in Chemistry

VOLUME=11

YEAR=2023

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2023.1113394

DOI=10.3389/fchem.2023.1113394

ISSN=2296-2646

ABSTRACT=<p><bold>Introduction:</bold> The effect of the functional group of the cation on SO2 acidic gas absorption by some designed amino acid ionic liquids (AAILs) was studied.</p><p><bold>Methods:</bold> An isolated pair of glycinate anion and pristine imidazolium-based cation, as well as decorated cation functionalized by hydroxyl (OH), amine (NH<sub>2</sub>), carboxylic acid (COOH), methoxy (OCH<sub>3</sub>), and acetate (CH<sub>3</sub>COO) groups, were structurally optimized by density functional theory (DFT) using split-valence triple-zeta Pople basis set.</p><p><bold>Results and Discussion:</bold> The binding and Gibbs free energy (ΔG<sub>int</sub>) values of SO<sub>2</sub> absorption show the AAIL functionalized by the COOH group is the most thermodynamically favorable green solvent and this functional group experiences the closest distance between anion and captured SO<sub>2</sub> and <italic>vice versa</italic> in the case of cation … SO<sub>2</sub> which may be the main reason for being the best absorbent; in addition, the highest net charge-transfer amount of SO<sub>2</sub> is observed. Comparing the non-covalent interaction of the systems demonstrates that the strongest hydrogen bond between captured gas and anion, as well as π-hole, and van der Waals (vdW) interaction play critical roles in gas absorption; besides, the COOH functional group decreases the steric effect while the CH<sub>3</sub>COO functional group significantly increases steric effect after absorption that declines the hydrogen bond.</p>