The advancements in mixed matrix membranes containing MOFs and ionic liquids for CO₂/N₂ separation

Carbon dioxide (CO₂) is the main greenhouse gas contributing to the rise in global temperature. Polymeric membranes often face a permeability-selectivity trade-off, limiting their effectiveness in meeting the demands of modern membrane technology. Mixed matrix membranes (MMMs) suggest advantages in energy consumption, cost, and operation for gas separation by overcoming the limitations of pure polymeric membranes through the incorporation of inorganic-organic hybrid material fillers. Our goal in this research was to improve the separation performance of polyvinyl chloride (PVC) membrane by creating an IL@AC/MOF filler by impregnating ionic liquid (IL) with an activated carbon/NH₂-MIL-53(Al) (AC/MOF) composite. This filler was then added to the PVC membrane, offering a possible way to address the trade-off problems in membranes of polymeric by fusing the high gas separation efficiency of inorganic fillers with the processability of polymers. TGA, FESEM, EDX, FTIR spectroscopy, X-ray Diffraction (XRD), and Brunauer-Emmett-Teller (BET) surface area analysis were used to characterize the produced MMMs. At pressures up to 4 bar for CO₂ and N₂, the permeability, diffusion coefficients, and solubility of MMMs were determined at 288.15, 298.15, 308.15, and 318.15 K. The results indicate that IL@AC/MOF/PVC MMMs with 15 wt.% IL@AC/MOF loading had CO₂ permeabilities that were 12.4 times greater than those of the PVC membrane. Furthermore, the CO₂/N₂ selectivity of IL@AC/MOF/PVC MMMs with 15 wt.% IL@AC/MOF loadings was 1.3 times greater than the selectivity of the pure PVC membrane at 298.1 5 K and 3 bar. The AC/MOF composite successfully improved gas diffusion in the PVC membrane owing to the porous nature of the MMM nanocomposites. The obtained data demonstrate that the separation performance of IL@AC/MOF/PVC MMMs is approached the Robeson upper-bound limit.