In-situ growth of zeolitic imidazolate framework-67 nanoparticles on polysulfone/graphene oxide hollow fiber membranes enhance CO₂/CH₄ separation

Zeolitic imidazolate frameworks (ZIFs) are attracting membrane-based gas separation researchers because of their exceptional and tunable physicochemical properties. In this study, a novel approach has been demonstrated to modify hollow fiber membranes (HFMs) by in-situ growth of ZIF-67 nanoparticles on the lumen side of polysulfone/graphene oxide (Psf/GO) HFMs. The formation of ZIF-67 nanoparticles on the HFMs was confirmed by different spectroscopy and microscopy techniques. The gas separation performance was measured by conducting experiments with pure gas and an equimolar mixture of CO₂ and CH₄, at 25 °C and 1–5 bar pressure. In the single gas permeation studies, ZIF-67 coated HFMs showed CO₂/CH₄ selectivity of 22.38 ± 0.30, which was almost 3.4 times the selectivity of the pristine HFMs. Furthermore, for equimolar CO₂/CH₄ mixture, though a slight decrease in CO₂ permeance was measured, ZIF-67 coated HFMs exhibited CO₂/CH₄ selectivity of 44.94 ± 3.00, which was 3.3 times the selectivity of the uncoated HFMs. Interestingly, ZIF-67 coated HFMs maintained their gas separation performance over a long duration. Thus, the novel in-situ grown ZIF-67 on Psf/GO HFMs showed improved CO₂/CH₄ separation performance, making these modified membranes potentially useful for the practical gas separation applications.