Ionic liquids(ILs) have received extensive attention, due to the unique physical and chemical properties, particularly the low vapor pressure, which provides a possibility of ILs, to be used as green solvents and to be widely applied to gas separation. In this paper,density functional theory is used to analyzing the influence of different polar solvents, as well as various anions basicity on the structure of ILs. Moreover, the theory of atoms in molecules(AIM) and natural bond orbital(NBO) analysis were applied to the absorption of small molecular gases by different ILs. Four parts are studied in the following:First, we perform a quantum mechanical calculations about three different polar solvents such as water(H2O), acetone(C3H6O), tetrahydrofuran(C4H8O) and various anion triflate(CF3SO3-) on the structure of triethylammonium methylsulfonate[Et3NH][CH3SO3](TEAMS) ILs at B3LYP/6-31+G** level of theory. Results find that the smallest number of the water molecules required to break the TEAMS is four, while it is three for TEATF, which the [CH3SO3]- anion is replaced by [CF3SO3]-. However, the TEAMS can exist at all solvent concentrations with decreasing polarity of the solvents.Moreover, NBO analysis confirms above discussion.Then, a quantum calculation is performed at M06-2X/6-31+G** level of theory to investigate the mechanisms of nitrogen dioxide gas(NO2) and nitrogen tetroxide(N2O4)captured by 1-ethyl-3-methylimidazolium trifluoromethanesulfonate [Emim][OTf] ILs,Meanwhile, AIM and NBO analysis are employed to interpret the origin of the interaction. Calculations show the attraction between the anion and NO2(or N2O4) is the dominant factor in determining the absorption process. In addition, the πcation-π bonds between the cation and the gas play an important role in absorption.After that, we studied the influences of 1-ethyl-3-methylimidazolium [Emim]+ cation,and trifluoromethanesulfonate [OTf]- anion on N2O4 isomerization at M06-2X/6-31+G**level of theory. AIM and NBO methods are also used to explain the phenomenon, the results show that anion of ILs can effectively reduce the activation.Finally, we have investigated the different types of ILs absorbing ammonia(NH3) at B3LYP/6-31++G** level of theory, explaining the selective adorption between ammonia and ILs. |