The thermophysical properties such as density, refractive index, and viscosity of five aprotic ILs bearing imidazolium (1-ethyl-3-methylimidazolium emim, 1-butyl-3-methylimidazolium bmim, 1-benzyl-3-methylimidazolium bnmim), pyrrolidinium (1-butyl-1methylpyrrolidinium bmpyr), and pyridinium (N-butylpyridinium bpyn) cations with 2-acryloamido-2-methylpropanesulfonate AMPS anion were studied, and their effect on CO2 solubility was explored. The density and viscosity were determined within the temperature range of (293.15 to 363.15) K at atmospheric pressure, while refractive indices were measured within the temperature range of (288.15 to 333.15) K. Among imidazolium cations, increasing the side chain length resulted in increased refractive index and viscosity with a corresponding decrease in density. In the presented ILs, emimAMPS showed the highest density and least viscosity over the entire temperature range and an enhanced CO2 dissolution of 0.40 mole fraction at 1 MPa was observed at 298.15 K. Moreover, the Henry's constant of emimAMPS was determined to be 1.957 MPa which was 49.5, 65.5, 21, and 53% less than bmimAMPS, bnmimAMPS, bmpyrAMPS, and bpynAMPS, respectively. The present study provides a better understanding of the structure-activity relationship between CO2 sorption and physicochemical properties of studied ILs. © 2017 American Chemical Society.