Connection between empty volume and solubility of light gases in [CnMIM][NTf2] ionic liquids

The connection between empty intermolecular volume and gas solubility has been widely discussed. Recently, interest in this issue has increased concerning ionic liquids (ILs). In this work, we study the mixtures of gases (CO2, O2, N2, CH4) with ionic liquids ([CnMIM][NTf2], n = 2, 4, 6, 8) using molecular dynamics simulations and the Voronoi-Delaunay method for the empty volume analysis. We have shown that the gas molecules locally loosen the IL, forming an additional empty volume in the mixture. However, the CO2 molecule adds a significantly smaller empty volume compared to O2, N2, and CH4 molecules. This fact correlates with their solubility: the solubility of CO2 is higher compared to other studied gases. The distributions of dissolved molecules near different components of ionic liquids have also been studied. We showed that CO2 molecules are located closer to the anions than other gases. (c) 2022 Elsevier B.V. All rights reserved.