Facilitated transport membrane with functionalized ionic liquid carriers for CO2/N2, CO2/O2, and CO2/air separations

CO2 separations from cabin air and the atmospheric air are challenged by the very low partial pressures of CO2. In this study, a facilitated transport membrane (FTM) is developed to separate CO2 from air using functionalized ionic liquid (IL) and poly(ionic liquid) (PIL) carriers. A highly permeable bicontinuous structured poly(ethersulfone)/poly(ethylene terephthalate) (bPES/PET) substrate is used to support the PIL-IL impregnated graphene oxide thin film. The CO2 separation performance was tested under a mixture feed of CO2/N2/O2/H2O. Under 410 ppm of CO2 at 1 atm feed gas, CO2 permanence of 3923 GPU, and CO2/N2 and CO2/O2 selectivities of 1200 and 300, respectively, are achieved with helium sweeping on the permeate side. For increased transmembrane pressure (>0 atm), a thicker PIL-IL/GO layer was shown to provide mechanical strength and prevent leaching of the mobile carrier. CO2 binding to the carriers, ion diffusivities, and the glass transition temperature of the PIL-IL gels were examined to determine the membrane composition and rationalize the superior separation performance obtained. This report represents the first FTM study with PIL-IL carriers for CO2 separation from air.