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 CO 2 separation membranes owing to its high density of ether groups, which preferentially facilitate CO 2 transport while hindering N 2 permeation. However, the highly cross-linked PEGDA membrane microstructure leads to low CO 2 permeability. Herein, ionic liquids (ILs), characterized by high CO 2 adsorption capacity, were incorporated into poly(ethylene oxide) (PEO) membranes to tailor the microstructure of the cross-linked network, aiming to enhance CO 2 permeability while maintaining high CO 2 /N 2 selectivity. Four types of ILs with different cations were employed for membrane fabrication. Among them, the [EMIM][Tf 2 N]-loaded PEO membrane exhibited the best separation performance, achieving a CO 2 permeability of 672 Barrer, 3-fold enhancement compared with the pristine cross-linked PEO membrane, while maintaining a CO 2 /N 2 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.