The quantum-chemical approach COSMO-RS was used to develop structure-property relationships of reversible ionic-liquid (RevIL) solvents for CO2 capture. Trends predicted for the thermodynamic properties of the RevILs using COSMO-RS, such as CO2 solubility, solvent regeneration enthalpy, and solvent reversal temperature, were verified by experimental data. This method was applied to a range of structures, including silylamines with varying alkyl chain lengths attached to the silicon and amine functionality, silylamines with fluorinated alkyl chains, sterically hindered silylamines and carbon-based analogues. The energetics of CO2 capture and release and the CO2 capture capacities are compared to those of the conventional capture solvent monoethanolamine. The results of this study suggest that the simple COSMO-RS computational approaches reported herein can act as a guide for designing new RevILs. COSMO-RS allows for the determination of the relative thermodynamic properties of CO2 in these and related systems.