Molecular Dynamics Investigation of Efficient SO 2 Absorption by Anion-Functionalized Ionic Liquids

Ionic liquids are appropriate candidates for the absorption of acid gases such as SO 2 . Six anion-functionalized ionic liquids with different basicities have been studied for SO 2 absorption capacity by employing quantum chemical calculations and molecular dynamics (MD) simulations. Gas phase quantum calculations unveil that the high uptake of SO 2 in these ionic liquids originates from the basicity of the anions and the consequent enhanced anion-SO 2 interactions. MD simulations of SO 2 –IL mixtures reveal the crucial role of both cations and anions in SO 2 dissolution. Multiple-site interactions of SO 2 with the anions have been identified. The calculated solvation free energy substantiates these observations. The order of computed Henry’s law constant values with change in the anion is in fair agreement with experimentally determined SO 2 solubility order. Graphical Abstract Efficient absorption of SO 2 by anion-functionalized ionic liquids has been studied using quantum mechanical and molecular dynamics simulation methods. Improved absorption capacity at much lower desorption cost has been found to be consequence of SO 2 -cation interaction via dispersion forces and multiple-site interactions of SO 2 with anions.