Recently, the use of ionic liquids (ILs) for carbon capture and separation processes has gained great interest by many researchers due to the high solubility of CO₂ in ILs. In the present work, solubility measurements of CO₂ in the novel IL 1-n-butyl-3-methylimidazolium nonafluorobutylsulfonate C₄mimCF₃CF₂CF₂CF₂SO₃ were performed with a high-pressure view-cell technique in the temperature range from 293.15 to 343.15 K and pressures up to about 4.2 MPa. For comparison, solubilities of H₂, N₂, and O₂ in the IL were also measured at 323.15 K via the same procedure. The Krichevsky-Kasarnovsky equation was employed to correlate the measured solubility data. Henry's law constants, enthalpies, and entropies of absorption for CO₂ in the IL were also determined and presented. The CO₂ solubility in this IL was compared with other ILs sharing the same cation. It was shown that the solubility of CO₂ in these ILs follows the sequence: C₄mimCF₃CF₂CF₂CF₂SO₃ ≈ C₄mimTf₂N > C₄mimCF₃CF₂CF₂COO > C₄mimBF₄, and the solubility selectivity of CO₂ relative to O₂, N₂, and H₂ in C₄mimCF₃CF₂CF₂CF₂SO₃ was 8, 16, and 22, respectively. Furthermore, this IL is regenerable and exhibits good stability. Therefore, the IL reported here would be a promising sorbent for CO₂.