A tough double-network ion gel membrane based on poly (ionic liquid) for efficient carbon capture

Ion gel membranes show great potential for carbon capture due to their excellent solubility selectivity for CO2. However, poor mechanical properties and limited stability as well as low gas permeability limit their application. Here, we report a environmentally friendly and simple strategy for preparing double-network(DN) ion gel membranes with both high strength and excellent gas separation performance. We use a "one-pot method" that the first network(FN) and the second network(SN) with ionic liquid were mixed evenly, and the DN membrane was prepared under heating and UV light. Wherein the FN was obtained by a ring-opening reaction between O, O-bis(2-aminopropyl) polypropylene glycol-block-polyethylene glycol-block-polypropylene glycol and a trimethylolpropane triglycidyl ether. And the SN was obtained by free radical polymerisation between 1 and vinyl-3-ethylimidazole bis(trifluoromethanesulfonyl)imide and a p-divinylbenzene (DVB) crosslinker. The crosslinking density of FN and SN, the mass ratio of the FN to the SN, as well as the content and type of free ionic liquid were optimized to improve the mechanical and gas separation properties of the DN membrane. When the crosslinking groups reacted quantitatively, the tensile strength of DN membranes is 1.5 MPa and the elongation at break is 120 %. With the increase of free ILs content, the crystallinity as well as the glass transformation temperature of the DN membrane decreases and the CO2 permeability increases (PCO2:866 Barrer α (CO2/N2):31). When 1-ethyl-3-methylimidazolium dicyanamide was used, the CO2/N2 separation performance can surpass the 2008 upper bound (PCO2:464 Barrer α (CO2/N2):63). The DN membrane has better gas separation and mechanical properties than the SN membrane and shows superior combination of the permeability and selectivity. This research provides a new approach designing a tough ion gel membrane which shows great potential for practical application in carbon capture.