Graphene-modified MIL-125-NH2 mixed matrix membranes for efficient H2 and CH4 purification

This study investigates the performance of the mixed matrix membranes (MMMs) incorporating hybrid fillers of metal-organic framework (MIL-125-NH2) and graphene nanosheets (GNs) for enhanced methane (CH₄) and hydrogen (H₂) separation in the purification sector. The physico-chemical properties of the MMMs were evaluated by SEM, XRD, FTIR, AFM, TGA, DTG, and Brunauer-Emmett-Teller. The permeability and selectivity of the MMMs were determined using different single gases (CO2, N2, H2, and CH4) at various temperatures (20-60 °C). Optimization of fabrication parameters resulted in a significant improvement in porosity and roughness of the fabricated MMMs. The permeabilities of the MOF/PES membrane are 20.3 (CO2), 23.9 (N2), 32.2 (CH4), and 24.1 (H2) x 104 Barrer, while incorporating 0.05 wt% of GNs into the MOF/PES membrane improved the permeability by 36 % (CO2), 41 % (N2), 31 % (CH4), and 370 % (H2). In addition, the H2/CO2 and H2/N2 selectivities of the MMMs significantly increased up to 4 and 3.3, with an improvements of 236 % and 230 %, respectively, compared to the MOF/PES membrane. Furthermore, the CH4/CO2 and CH4/N2 selectivities of the MMMs decreased by 4 %. Therefore, a hybrid filler (10 wt % of MIL-125-NH2 and 0.05 wt % of GNs is highly recommended to improve the permeability and selectivity of the PES membrane, expanding its potential applications in CH4 and H2 purification.