Carbon dioxide interaction with a series of ionic liquids consisting of fluorophenyltrifluoroborate anions studied by in situ ATR-FTIR spectroscopy

[Display omitted] •Room temperature ionic liquids with new fluorophenyltrifluoroborate anions.•In situ ATR-FTIR spectroscopy was used to study CO2 sorption in a ILs with fluorophenyltrifluoroborate anions.•DFT method and IGMH analysis were used to calculate the non-covalent interactions between CO2 and ILs.•The splitting degree of the ν2 mode of CO2 is not correlated with the interaction energy of CO2 and ILs. Fluorinated ionic liquids have new and unique properties by combining the properties of highly fluorinated compounds and ionic liquids. In this work, the interaction of CO2 with ionic liquids containing fluorophenyltrifluoroborate anions ([BMIM][C6H5BF3], [BMIM][4-F-C6H4BF3], [BMIM][C6F5BF3], [BMIM][4-BuO-C6F4BF3]) has been studied for the first time using high-pressure in situ ATR-FTIR spectroscopy. Analysis of the IR spectra of ionic liquids recorded under CO2 pressure showed disaggregation of alkyl groups and a slight decrease in cation–anion interaction, based on the appearance of a blue shift of absorption bands characteristic of stretching vibrations of CH bonds in alkyl groups, aromatic and imidazolium rings. It was found that fluorination of the phenyl group and introduction of a butoxy group significantly increased the solubility of CO2. The enthalpy and entropy of CO2 dissolution also increase with the increase of fluorine atoms in the anion. Theoretical calculations using the DFT method also showed an increase in the energy of interaction of CO2 with ionic liquids with an increase in the number of fluorine atoms. The use of an independent gradient model based on Hirshfeld partition (IGMH) analysis allowed the patterns of splitting of the CO2 bending ν2 mode to be explained. It was found that in this series of ionic liquids, the degree of the splitting of the CO2 bending mode depends on the contributions of the CO2 atoms to the interaction with the ionic liquid, rather than on the interaction energy.