Ultrathin, Highly Permeable Graphene Oxide/Zeolitic Imidazole Framework Polymeric Mixed-Matrix Composite Membranes: Engineering the CO₂-Philic Pathway

High-performance, thin-film mixed-matrix membranes (MMMs) on a porous support have been developed, using zeolitic imidazole framework (ZIF) decorated graphene oxide (GO) as a filler, dispersed in a poly(vinyl imidazole)-co-poly(oxyethylene methacrylate) (PVI-POEM) copolymer matrix. The low gas permeance of the neat GO-filler-based MMM was significantly improved by routing a CO2-permeable pathway through the semi-interconnected GO-ZIF nanocages. The good rubbery adhesion properties of PVI-POEM, together with the chemical similarity between PVI and the ZIF imidazole linker, induced excellent polymer/filler interface engineering in the GO-ZIF MMMs. Moreover, the GO-ZIF nanofillers were fully blanketed by the PVI-POEM copolymer, to prevent interfacial defects, while in turn an ultrathin, highly permeable GO-ZIF selective layer was formed. As a result, the GO-ZIF 5% composite MMM achieved a state of the art CO2 permeance of 995.1 GPU, retaining excellent CO2/N2 and CO2/CH4 selectivities of 45.9 and 17.5, respectively. The CO2-philic pathway of GO-ZIF filler and good interaction bewteen the PVI-POEM and GO-ZIF generate a synergistic effect of CO2 separation, in comparison with a neat PVI-POEM composite membrane (CO2 permeance 626.4 GPU, CO2/N2 selectivity 36.2).