Computational study of toluene capture by imidazolium-based ionic liquids paired with acetate, tetrafluoroborate and hexafluorophosphate anions

In this study, the capture of toluene by imidazolium-based ionic liquids (ILs) paired with acetate, tetrafluoroborate, and hexafluorophosphate anions was theoretically investigated. The geometries of the anions, cations, and ion pairs were analyzed, and the most stable structures for toluene adsorption were identified. The interaction energy of the ion pair–toluene complex and binding energy for the most stable structures were calculated. It was found that acetate-containing ILs exhibited the highest interaction and binding energies. For acetate-containing ILs, both the ion pair–toluene interaction energy and binding energy increased with the elongation of the alkyl chain. Molecular Electrostatic Potential (MEP) surfaces were generated to identify the ion pair sites that preferentially interact with toluene. The ion pair–toluene interactions in the most stable structures were examined using Natural Bond Orbital (NBO) analysis. Finally, non-covalent interactions between ion pairs and toluene were analyzed using Non-Covalent Interaction (NCI) analysis. This study underscores the critical influence of anion selection and alkyl chain modification in tailoring ILs for efficient toluene capture, offering valuable guidelines for the rational design of ILs in environmental and industrial applications.