A Mini-Review of Metal–Organic Frameworks and Polymers in Mixed Matrix Membranes for CO2 Gas Separation

The increasing global anthropogenic CO 2 ​ emissions necessitate the development of efficient carbon capture technologies. While polymeric membranes offer an energy-efficient approach to gas separation, their performance is restricted by the Robeson upper bound—the inherent trade-off between permeability and selectivity. To overcome this limitation, mixed matrix membranes (MMMs) incorporating metal-organic frameworks (MOFs) have emerged as an effective strategy. This review paper explores the design and performance advancements of MOF-based MMMs for CO 2 ​ separation (such as CO 2 /CH 4 ​ and CO 2 /N 2 ​ systems). Capitalizing on the exceptional specific surface area (up to 3000 m 2 g −1 ), pore architecture, and structural flexibility of MOFs, these membranes combine the processability of polymers (both glassy and rubbery) with the molecular sieving properties of inorganic fillers. Furthermore, fabrication techniques for flat sheet configurations are discussed. Despite successful outcomes in surpassing the Robeson limit, this paper emphasizes that challenges such as scale-up complexities and long-term stability remain. Finally, the necessity of cost optimization, the development of hybrid systems, and continuous manufacturing methods for the application of these membranes in natural gas sweetening and post-combustion processes is highlighted.