Fabricating High-Performance Polyimide/DD3R Mixed Matrix Carbon Molecular Sieve Membrane for CO ₂ Capture

Mixed matrix carbon molecular sieve membranes are gas separation membranes that combine the synergistic effects of carbon molecular sieves and inorganic components. The DD3R molecular sieve exhibits significant molecular size sieving effects and demonstrates high adsorption selectivity toward CO 2 . Against the backdrop of the current push for carbon neutrality, highly efficient CO 2 separation materials are of great significance to the development of carbon capture and storage (CCS) technology. This is particularly true in natural gas purification and industrial exhaust gas treatment, where higher demands are placed on the efficient separation of CO 2 and CH 4 . Based on this, this study used the DD3R molecular sieve as the functional filler, used 6FDA-DAM polyimide as the precursor, and obtained the hybrid matrix carbon membrane through a high-temperature carbonization process. The microstructure and physicochemical characteristics of the carbon membranes were systematically characterized using scanning electron microscopy and other techniques, and the effect of DD3R loading on their gas separation performance was investigated. The results indicate that as the doping concentration of DD3R molecular sieves increases, both the CO 2 permeability and CO 2 /CH 4 separation selectivity of the mixed matrix carbon molecular sieve membranes exhibit a trend of initially increasing and then decreasing. Furthermore, when the DD3R doping mass fraction reached 0.3 wt %, the prepared carbon membrane exhibited optimal performance, achieving a CO 2 permeability coefficient of 29,679 Barrer and a CO 2 /CH 4 selectivity of 33.1, surpassing the Robeson upper limit reported in 2019. The results indicate that, owing to the unique pore structure of the DD3R molecular sieve and its synergistic interaction with the carbon matrix, the carbon membrane effectively overcomes the trade-off between permeability and selectivity, demonstrating significant potential for industrial applications and holding broad prospects in the field of carbon capture.