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

Abstract

A novel strategy for efficient CO2 capture by tuning the strength of cation coordination interactions of alkali metal chelated dual functional ionic liquids (DFILs) is reported. CO2 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 CO2 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 CO2 capture capacity than other DFILs, with an extremely high capacity of CO2 (∼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 CO2 capacity originates from the fact that both [K(DGA)2]+ and [Im]− of [K(DGA)2][Im] react with CO2. Moreover, [Im]− reacts preferentially with CO2 over [K(DGA)2]+.