Exploring the Effect of Different Anions and Cations on the Solubility of CO₂ in Nitrile Imidazolium-Based Ionic Liquids with Sulfonated-Based Anions

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 (ΔH⁰, ΔS⁰, ΔG⁰). In addition, the CO₂/CH₄ solubility selectivity was determined.