CO₂ separation performance and thermo-mechanical characteristics of mixed matrix membranes composed of polyvinylidene fluoride/hyperbranched polyethylenimine embedded with zinc oxide/graphene oxide filler

Herein, polyvinylidene fluoride (PVDF)/hyperbranched polyethylenimine (HPEI) blend matrix was infused with graphene oxide–zinc oxide (GO–ZnO) filler to fabricate mixed matrix membranes (MMMs). These membranes were investigated by dynamic mechanical–thermal analysis (DMTA), single and binary gas (CO₂/N₂ and CO₂/CH₄) experiments and for anti-plasticization performance. Varying loading fractions [0.1%, 0.3%, 0.5% and 0.7% (by weight)] of as-synthesised GO–ZnO filler were incorporated into the blend matrix (PVDF/HPEI). Utmost consideration was provided to understand the microstructure of MMMs through DMTA and its influence on gas separation performance. Single gas testing revealed that MMMs exhibited ~ 82% improved CO₂ permeability as compared to the control membrane, at 0.5% (by weight) GO–ZnO filler loading. During binary gas experiments, CO₂ permeability increased by 79%, whereas CO₂/N₂ and CO₂/CH₄ selectivity was enhanced by 136% and 142%, respectively. The highly CO₂-phillic amine moieties of HPEI and the polar oxygen-containing moieties on GO sheets augmented the CO₂ diffusivity and sorption. Amongst various membranes, MMMs loaded with 0.5% (by weight) GO–ZnO tested at various pressures (4, 6, 8 and 10 bars) demonstrated the highest inhibitory effect on the CO₂-induced plasticization. DMTA suggested that GO–ZnO created a robust interfacial adhesion with PVDF/HPEI, forming a rigid microstructure that was propitious in resisting pressure-induced plasticization. With a significant boost in thermo-mechanical attributes and CO₂ separation efficiency, GO–ZnO-loaded MMMs suggest intriguing prospects in CO₂ separation applications.