Tailoring the Microstructure of Cross-Linked PEO Membranes via Green Ionic Liquids for CO ₂ /N ₂ Separation

Photopolymerization of poly(ethylene glycol) diacrylate (PEGDA) has been broadly adopted for the fabrication of CO2 separation membranes owing to its high density of ether groups, which preferentially facilitate CO2 transport while hindering N2 permeation. However, the highly cross-linked PEGDA membrane microstructure leads to low CO2 permeability. Herein, ionic liquids (ILs), characterized by high CO2 adsorption capacity, were incorporated into poly(ethylene oxide) (PEO) membranes to tailor the microstructure of the cross-linked network, aiming to enhance CO2 permeability while maintaining high CO2/N2 selectivity. Four types of ILs with different cations were employed for membrane fabrication. Among them, the [EMIM][Tf2N]-loaded PEO membrane exhibited the best separation performance, achieving a CO2 permeability of 672 Barrer, 3-fold enhancement compared with the pristine cross-linked PEO membrane, while maintaining a CO2/N2 selectivity of 52. Furthermore, the membrane demonstrated stable separation performance under high-pressure conditions, after bending deformation, during a 120 h continuous operation test, and in mixed-gas separation experiments.