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Carbon dioxide (CO2) was revealed as a major greenhouse gas,and thus in recent years many techniques for its separation,capture,and storage have received increasing attention.CO2 capture is expected to become an important part of the future power production.Current technology for CO2 capture is very energy demanding.In order to make this process feasible and sustainable new technology must be developed.Existing concepts of CO2 capture are based on the absorption of CO2 in aqueous solutions of alkanolamines,ammonia,or potassium carbonate.There are needs to develop smarter technologies for CO2 capture.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.CO2 solubilities for various kinds of ionic liquids have been extensively measured for the past several years in our laboratory to examine the feasibility of using ionic liquids as CO2 capture media.Solubilities of CO2 in ionic liquids were determined by measuring bubble point pressures of the CO2 + ionic liquid mixtures of different compositions in a range of temperature using a high-pressure apparatus equipped with a variable-volume view cell.As target cations consisting of ionic liquids,we examined imidazolium-,pyrrolidinium-,piperidinium-,quaternary ammonium-,phosphonium-,and aminoalkylimidazolium-based cations with different kinds and lengths of alkyl chains.The anions studied in this work were bis(trifluoromethylsulfonyl)imide,trifluoromethanesulfonate,methanesulfonate,methylsulfate,trifluoroacetate,dicyanamide,etc.It was found that the selection of different combinations of anions and cations had a big influence on the CO2 absorption capacities.The increase in the alkyl chain length on the cation increased the CO2 solubility.The phase equilibrium data for the CO2 + ionic liquid systems were correlated using the Peng-Robinson equation of state.The critical properties and acentric factors were estimated by the modified Lydersen-Joback-Reid group contribution method proposed by Valderrama and Rojas.For each system,the optimum values of the binary interaction parameters of the PR-EoS were obtained and the comparison of the experimental values with the modeling results was investigated.