The thermophysical properties (decomposition temperature, glass transition temperature, density, and viscosity) of imidazolium-based ionic liquids (ILs) paired with the tricyanomethanide ([TCM]⁻) anion and the bis(trifluoromethylsulfonyl)imide ([Tf₂N]⁻) anion were studied within a wide temperature range. The effect of the ether functional group (in [Tf₂N]⁻ and [TCM]⁻ ILs) and hydroxyl functional group (in [Tf₂N]⁻ IL) incorporated in the cation’s alkyl chain on the thermophysical behavior and carbon dioxide (CO₂) solubility was evaluated by comparing their behavior to the corresponding nonfunctionalized ILs. The thermal stability was enhanced by the inclusion of hydroxyl functionalization in the cation’s alkyl chain while ether functionalization had no major effect on the thermal stability. The ether groups (one or two) resulted in an increase in the density and a decrease in the viscosity of all ILs. The hydroxyl group resulted in an increase in both properties. The CO₂ solubilities were not affected by the presence of the ether groups, while the hydroxyl group led to a significant decrease in the solubility. Additionally, the electrolyte perturbed-chain statistical associated fluid theory (ePC-SAFT) equation of state was used to calculate the CO₂ solubility in the ILs and the Henry’s law constant. The model showed great predictive ability. The Henry’s constants were applied to calculate the partial molar thermodynamic properties of solvation.