CO2 capture by fluorinated-imidazolium based ionic liquids: a multiple minima hypersurfaces analysis

Ionic liquids (ILs) are a promising alternative for CO 2 capture, offering high stability, environmental friendliness, and scalability. The present theoretical study focused on the evaluation of 12 ILs for the capture of up to 5 CO 2 molecules. The 12 ILs are based on imidazole and fluorine, C 8 H 4 F 13 mim + BF 4 − , C 8 H 4 F 13 mim + TFO − , Dmim + BF 4 − , Dmim + TFO − , Hmim + FAP − , Dbim + FAP − , Hmim + methide − , Dbim + methide − , Hmim + (PFOc)SO 3 − , Omim + (PFOc)SO 3 − , Hmim + (PFBu)SO 3 − , and Omim + (PFBu)SO 3 − . A stochastic dynamic search algorithm was used to generate the structure of the nCO 2 -IL clusters, with n = 1 to 5. The molecular clusters were then optimized using Density Functional Theory (DFT) calculations to describe the nature of the interactions between the 12 ILs and CO 2 . Results show that CO 2 physisorps and preferentially interacts with anions, also fluorine substitution increasing CO 2 affinity. Cluster formation is exothermic and favored at lower temperatures. The physisorption is driven by weak van der Waals interactions. The Dbim + FAP - , C 8 H 4 F 13 mim + BF 4 − and C 8 H 4 F 13 mim + TFO − ILs demonstrated the highest CO 2 binding capacity but at the simulated conditions the process is not spontaneous. These findings are useful for designing efficient CO 2 capture materials based on ILs.