Unraveling weak interactions between fluorinated gases and ionic liquids

The efficient capture of fluorinated gases (F-gases) such as hexafluoroethane (R116) and 1,1,1,2-tetrafluoroethane (R134a) is critical owing to the high global warming potential of these species. Considering the potential of ionic liquids (ILs), especially fluorinated ILs (FILs), for capturing F-gases, in this study we systematically investigated the structure-property relationship between thermodynamic behaviors and weak interactions in F-gas/FIL systems. We focused on two cations, 1-octyl-3methylimidazolium ([OMIM](+)) and 1-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)-3-methylimidazolium ([FOMIM](+)), and two anions, bis(trifluoromethylsulfonyl)amide ([Tf2N]) and bis(pentafluoroethylsulfo nyl)amide ([BETI]). The effects of the IL structure on the gas-liquid equilibrium (GLE) of F-gas/FIL systems were elucidated by analyzing the experimental solubility data. The results indicate that while both the fluorinated cation and anion can enhance the solubility of F-gases, the contribution of the fluorinated cation to the increase in solubility is larger than that of the fluorinated anion. The relationship between GLE behavior and weak interactions of F-gas/FIL systems was determined by performing quantum chemical calculations. (C) 2021 Elsevier Ltd. All rights reserved.