The solubility data of carbon dioxide (CO2) in a series of ionic liquids (ILs): 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM](+)[BF4](-)), 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM](+)[BF4](-)), 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([OMIM](+)[Tf2N](-)), and their binary mixtures (i.e., [EMIM](+)[BF4](-) + [OMIM](+)[Tf2N](-) and [BMIM](+)[BF4](-) + [OMIM](+)[Tf2N](-)) at temperatures (313.2 and 333.2) K and pressures up to 6 MPa were measured by a high-pressure view-cell technique. The mixed ILs tested were (0, 20, SO, 80, and 100) wt % [EMIM](+)[BF4](-) (or [BMIM](+)[BF4](-)) in [OMIM](+)[Tf2N](-). The solubility data of CO2 in pure ILs were correlated with the Peng-Robinson equation of state (PR EOS), whereas the solubility data of CO2 in mixed ILs can be well predicted based on the mole fraction average of [EMIM](+)[BF4](-) (or [BMIM](+)[BF4](-)) and [OMIM](+)[Tf2N](-) over the solubility of CO2 in pure ILs. It was found that the solubility of CO2 in pure or mixed ILs increases with increasing pressure at all temperatures but decreases with increasing temperature. The Henry's constants follow the order of [BMIM](+)[BF4](-) + [OMIM](+)[Tf2N](-) > [EMIM](+)[BF4](-) + [OMIM](+)[Tf2N](-) at the same content of [OMIM](+)[Tf2N](-). The use of mixed ILs provides the opportunity to tune the solubility and selectivity for capturing CO2 at high pressures. It is the first work for us to present the solubility data of CO2 in binary mixtures of ILs at high pressures for physical absorption.