The effect of different cations and anions on the CO2 solubility in ionic liquids was investigated using a systematic approach in the current work. Four ionic liquids (ILs) containing the same cation (C2CN Bim) were synthesized, each incorporating a different anion (DDS, BS TFMS, and DOSS). In addition, four ILs with different cations (C2CN Bim, C2CN Him, C2CN Oim, and C2CN Dim) were prepared, all containing the same anion (DOSS). Then, these ILs were characterized and utilized to determine how various cations and anions influence CO2 solubility. The prepared ILs were characterized using NMR and elemental analysis. Impurities, such as moisture and halide content were also determined. The CO2 solubility was studied using the gravimetric method (MSB) at pressures of 1, 5, 10, 15, and 20 bar. An investigation was also conducted to examine the influence of temperature on the solubility of CO2 in C2CN Dim DOSS. Henry�s law constants were calculated along with the thermodynamic properties such as standard enthalpy, entropy, and Gibbs free energy (�H0, �S0, �G0). In addition, the CO2/CH4 solubility selectivity was determined. © The Author(s), under exclusive licence to Korean Institute of Chemical Engineers, Seoul, Korea 2024.