Highly CO2 selective membranes by potassium cations as carriers for facilitated transport with Ag2O particles and free ions in ionic liquid

- CO2 separation membranes consisting of ionic liquid BMIMBF4/Ag2O/KF composite.
- Potassium cations as CO2 carriers for facilitated transport.
- Enhanced solubility of CO2 molecules by both Ag2O particles and free ions in ionic liquid.

The highly selective composite membranes consisting of ionic liquid 1-butyl-3-methyl imidazolium tetrafluoroborate (BMIM+BF4−)/Ag2O/KF were prepared for CO2 separation. When Ag2O and KF were incorporated into BMIM+BF4−, the ideal selectivities of CO2/N2 and CO2/CH4 reached 105 and 52, respectively, with a CO2 gas permeance of 31 GPU. These enhanced separation performance were attributable to synergistic effect of (1) K+ cations in KF as CO2 carriers for facilitated transport and (2) the oxide layer of the well-dispersed Ag2O and free ions in ionic liquid for improvement in CO2 solubility. The coordinative interactions in the BMIM+BF4−/Ag2O/KF membrane were characterized by TGA, XPS, and FT-Raman spectroscopy.