Solubility data of carbon dioxide (CO2) in 1-ethyl-3-methylimidazo-lium trifluoromethanesulfonate [EMIM][TFO] at T = (273.15 to 413.15) K and in 1-butyl-3-methylimidazolium trifluoromethanesulfonate [BMIM][TFO] at T = (283.15 to 413.15) K with pressures up to p = 4.5 MPa are experimentally studied using an isochoric method. The temperature step is Delta T = 20 K. The measurements were at four different pressure steps from around 4.5 MPa to around 0.5 MPa. The CO2 solubility decreased with increasing temperature in both ionic liquids (ILs). The measurement ranges are in [EMIM][TFO] from a mole fraction x = 0.0274 and a corresponding molality m = 0.1083 mol.kg(-1) at T = 413.15 K and p = 0.415 MPa up to x = 0.5021 and m = 3.8749 mol.kg(-1) at T = 293.15 K and p = 3.995 MPa. The same measurements for [BMIM][TFO] are from a mole fraction x = 0.0304 and a corresponding molality m = 0.1087 mol.kg(-1) at T = 413.15 K and p = 0.423 MPa, up to x = 0.5663 and m = 4.5297 mol.kg(-1) at T = 293.15 K and p = 4.254 MPa. CO2 is more soluble in [BMIM][TFO] than in [EMIM][TFO] at a constant temperature. The temperature dependence of Henry's law constant was calculated and was always smaller than +/- 1%. The various thermodynamic properties, such as the Gibbs energy of solvation, the enthalpy of solvation, the entropy of solvation, and the heat capacity of solvation, were calculated from the experimental results. Obtained experimental values were compared with available literature results.