Advancing CO₂ separation performance in mixed matrix membranes via synergistic MOF@LDH Nanofillers

Membrane-based gas separation is widely regarded as a sustainable and environmentally friendly approach to mitigating CO₂ emissions, a key driver of climate change. However, permeability, selectivity trade-off and plasticization are major challenges faced. Mixed matrix membranes (MMMs) with advanced hybrid filler incorporation could exhibit great potential in gas separation applications. Here we report novel MMMs containing a hybrid filler synthesized via the in-situ growth of Cu-BTC MOF (Cu-MOF) on the uniform MgAl-CO₃ (M-LDH) nanosheets. The synthesized hybrid MOF-LDH (Cu-M HB) showed superior physicochemical stability compared to both M-LDH and Cu-MOF. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and thermogravimetric analysis (TGA) were employed to investigate the structural compatibility and interfacial integrity between the polymer and hybrid filler. The gas separation performance of pure Pebax membrane and MMMs at different hybrid nanofiller loading (1, 3, and 5 wt%) was evaluated at 1 bar to optimize the MMMs composition. Furthermore, the best-performing MMM was tested at different operating pressures (1–5 bars) to understand its effect on gas separation behaviour. Among the studied compositions, 1 wt% Cu-M HB/Pebax MMM exhibits the best gas separation performance achieving the highest CO₂/N₂ selectivity of 89.50 with moderate CO₂ permeability of 96 Barrer relative to pure Pebax membrane. This study illustrates the potential of hybrid fillers in fabricating different MMMs with enhanced gas separation performance.