Prediction of CO2 chemical absorption isotherms for ionic liquid design by DFT/COSMO-RS calculations

Ionic liquids with an aprotic heterocyclic anion (AHA-ILs) is a promising family of compounds to overcome the challenge of CO2 capture. In this work, a computational methodology has been developed to predict CO2 chemical absorption isotherms in AHA-ILs without the need of experimental data. This methodology combines DFT and COSMO-RS calculations allowing the design of new chemical absorbents for CO2 capture. The CO2 physical absorption equilibrium constants (Henry's law constants), chemical equilibrium constants and reaction enthalpies were reliably predicted by proposed computational approach, by means of comparison to available experimental data of 9 different AHA-ILs. Finally, 15 newly designed AHA-ILs were evaluated to demonstrate the flexibility of the DFT/COSMO-RS tool by predicting their CO2 absorption isotherms. The evaluated absorbents compromise very different behaviors: from physical absorption to reactions completely displaced toward products at very low CO2 partial pressure, emphasizing the extremely tunable character of AHA-ILs. Current results will definitively contribute to link molecular and processes scales in the research of new CO2 capture technology based on ILs.