Ionic liquids (ILs), vary strongly in their interaction with CO2. We suggest simple theoretical approach to predict the CO2 absorption behavior of ILs. Strong interaction of the CO2 with the IL anions corresponds to chemical absorption whereas weak interaction indicates physical absorption. A predictive estimate with a clear distinction between physical and chemical absorption can be simply obtained according to geometries optimized in the presence of a solvation model instead of optimizing it only in gas phase as has been done to date. The resulting Gibbs free energies compare very well with experimental values and the energies were correlated with experimental capacities. Promising anions, for ionic liquids with reversible CO2 absorption properties can be defined by a reaction Gibbs free energy of absorption in the range of -30 to 16 kJ mol(-1).
Keywords: absorption; carbon dioxide; computer chemistry; ionic liquids.
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