Development of an ion gel membrane containing a CO2-philic ionic liquid in interpenetrating semi-crystalline and crosslinkable polymer networks

We developed a tough and highly CO2-permeable ion gel membrane composed of a CO2-philic ionic liquid (IL), 1-ethyl-3-methylimidazolium tetracyanoborate ([Emim][B(CN)4]), and an interpenetrating polymer network (IPN) composed of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and crosslinkable poly(ethyl acrylate-co-N-succinimide acrylate) (poly(EA-co-NSA)). The semi-crystalline PVDF-HFP and IL-philic poly(EA-co- NSA) networks endowed the ion gel membrane with high mechanical strength and good IL-holding properties. The high mechanical strength and good IL-holding properties achieved by the polymer networks provided the ion gel membrane with high and selective CO2 permeability under pressurized conditions at a trans-membrane pressure difference of 250 kPa. In addition, the high CO2 absorbability of [Emim][B(CN)4] provided the ion gel membrane with a CO2 permeability of more than 2500 barrer and a CO2/N2 permselectivity of approximately 20 at an elevated temperature of 80 degrees C. It was also demonstrated that the CO2 permeability of the IPN ion gel membrane increased with increasing IL content. The IPN ion gel membrane with an IL content of 85 wt% had a CO2 permeability of 2243 barrer and a CO2/N2 permselectivity of 43 at 30 degrees C. The excellent CO2 permeability and CO2/N2 permselectivity were not changed by physical aging for more than one week.