The high-pressure vapor-liquid equilibrium for the binary systems of carbon dioxide (CO2) and a series of 1-alkyl-1-methyl pyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquids ([C(n)C(1)p(yr)][NTf2] (n = 3,4,6)) are reported at 298.15, 318.15, and 338.15 K and at pressures of up to 20 MPa. Experiments were conducted using gravimetric (IGA and XEMIS microbalances) and volumetric (high-pressure view cell) methods. The solubility of CO2 in pyrrolidinium ionic liquids increases with decreasing temperature and increasing pressure. The CO2 solubility also slightly increases with increases in alkyl chain length on the pyrrolidinium cation. The molar volume and volume expansion of CO2 + IL mixtures are also reported. The Fickian diffusion of CO2 in pyrrolidinium-based ionic liquids (similar to 10(-10) m(2).s(-1)) was calculated at pressures of up to 2 MPa and found to be slightly lower than the diffusivity of CO2 in an imidazolium-based ionic liquid with the [NTf2] anion.