Propylene/propane selective mixed matrix membranes with grape-branched MOF/CNT filler†
In this study, we fabricated mixed matrix membranes (MMMs) comprising a novel carbon nanotube/metal–organic framework (MOF) filler for efficient propylene/propane separation. Tomographic focused ion beam scanning electron microscopy was applied to quantitatively evaluate the filler dispersion and filler/polymer interfacial void ratio. The dispersion of ZIF-8 in MMMs was improved by the confined growth of ZIF-8 on the carbon nanotube (CNT) surfaces, yielding a simultaneous enhancement of C3H6 membrane permeability and C3H6/C3H8 selectivity. Excellent adhesion between the synthesized ZIF-8/CNT fillers and polymer matrix is observed, with only 0.086% void volume fraction, even at a high filler loading. The in situ growth of MOFs on CNTs shown here can provide an effective way to design mixed matrix membranes with improved filler dispersion, structural features and separation performance.