Carbon dioxide (CO2) was revealed as a major greenhouse gas,and thus in recenttm years many techniques for its separation,capture,and storage have received increasing attention.Ionic liquids having high thermal stability,negligible vapor pressure,and capability of selectively absorbing specific gases have been proposed as new CO2 capturing solvents which may potentially replace aqueous amines [1].Solubilities of CO2 in the ionic liquid phase (various types of ionic liquids) were determined by measuring bubble pressures of the CO2 + ionic liquid mixtures of different compositions at known temperatures using a high-pressure equilibrium apparatus equipped with a variable-volume view cell [2-5].For various types of ionic liquids,the effect of cations and anions in the ionic liquids on the CO2 solubility was studied.Imidazolium-,pyridinium-,and pyrrolidinium-based carious with different kinds and lengths of alkyl chains were selected as target cations.The anions studied in this work were bis(trifluoromethylsulfonyl)imide,trifluoromethanesulfonate,methanesulfonate,etc.The equilibrium pressure increased very steeply at high CO2 compositions.The increase in the alkyl chain length on the cation increased the CO2 solubility.The anion also appeared to play a significant role in determining the CO2 solubility.The ionic liquids that contain a level of fluorination improved the CO2 solubility.The anion with more fluoroalkyl group gave higher CO2 solubility.