Dual-Layer PDMS/Polysulfone Composite Membranes Incorporating Cu-MOF-74 for Enhanced CO2 Capture Performance

Polymeric membranes are widely investigated for CO2 separation; however, their performance is often limited by the permeability–selectivity trade-off. Incorporating metal–organic frameworks (MOFs) and designing composite membrane architectures are promising strategies to overcome these limitations. This study aims to evaluate the effect of incorporating MOF-74 (Cu and Ni variants) into a polydimethylsiloxane (PDMS) selective layer supported on a polysulfone (PSF) membrane for enhanced CO2/N2 separation performance. Dual-layer PDMS/PSF composite membranes were fabricated via phase inversion for the PSF support, followed by solution casting of the PDMS/MOF layer. The developed membrane architecture introduces a synergistic design that combines the mechanical robustness of PSF with the selective transport capability of PDMS and the strong CO2 affinity of MOF-74, offering an effective strategy for improving gas separation efficiency. Gas permeation performance was assessed using single-gas CO2 and N2 measurements at feed pressures of 2–5 bar. The incorporation of MOF-74 improved CO2 transport properties, with the 1 wt.% Cu-MOF-74 composite membrane achieving a CO2 permeance of 912.5 GPU and a CO2/N2 ideal selectivity of 94.75. The dual-layer configuration significantly enhanced permeance compared with unsupported mixed-matrix membranes while maintaining selectivity. Additionally, the composite membranes exhibited improved mechanical strength due to the PSF support layer. The findings demonstrate that dual-layer PDMS/PSF composite membranes incorporating MOF-74 provide a promising proof-of-concept approach for improving CO2 separation performance. Further studies involving mixed-gas testing and long-term stability are required to assess their practical applicability.