Tuning the strength of cation coordination interactions of dual functional ionic liquids for improving CO2 capture performance

A novel strategy for efficient CO 2 capture by tuning the strength of cation coordination interactions of alkali metal chelated dual functional ionic liquids (DFILs) is reported. CO 2 absorption and viscosity experiment, quantum-mechanical calculations showed that the strengthening of the coordination interactions between alkali metal ions and alkanolamine ligands of DFILs containing imidazolide anion ([Im] − ) leads to improve the stability of the cheated cation and weaken the chelated cation-anion interaction, resulting in efficient CO 2 capture capacity and reducing the viscosity of DFILs. Particularly, [K(DGA) 2 ][Im] has the stronger cation coordination interactions and lower viscosity (249.8 mPa∙s), exhibiting more efficient CO 2 capture capacity than other DFILs, with an extremely high capacity of CO 2 (∼1.37 mol/mol) in 15 min at T  = 333.2 K under atmospheric pressure and good reversibility (5 recycles). Spectroscopic investigations and quantum-mechanical calculations showed that such high CO 2 capacity originates from the fact that both [K(DGA) 2 ] + and [Im] − of [K(DGA) 2 ][Im] react with CO 2 . Moreover, [Im] − reacts preferentially with CO 2 over [K(DGA) 2 ] + .