Alireza Bahrami, Ahmadreza Raisi
This study explores mixed matrix membranes (MMMs) comprising polyurethane (PU), polycarbonate (PC), and ZIF-8 nanoparticles, focusing on how interactions among these components influence gas-separation properties. PU, synthesized via bulk polymerization, features a characteristic microphase-separated structure composed of soft segments that promote gas solubility and permeability and hard segments that provide mechanical stability and limit gas transport. Blending PC with PU modulates the microphase separation, further tuning the balance between permeability and selectivity. The incorporation of ZIF-8 nanoparticles enhances the free volume and creates preferential pathways for CO 2 , while also improving interfacial compatibility between the polymer phases. Comprehensive characterizations (FTIR, XRD, FESEM, and TEM) confirmed the successful synthesis and integration of ZIF-8 in the MMMs. Gas permeation experiments showed that incorporating 4 wt.% ZIF-8 into a PU/PC (75/25 wt.%) blend nearly doubled CO 2 /N 2 selectivity and increased CO 2 permeability by 25%. Higher ZIF-8 loadings (8–12 wt.%) further increased CO 2 permeability by up to 27%, with PU membranes containing 12 wt.% ZIF-8 achieving the highest CO 2 permeability (223.39 Barrer). Meanwhile, PC-rich membranes exhibited the highest selectivity (CO 2 /N 2 = 231.71; CO 2 /CH 4 = 123.69). The ternary MMMs composed of 25 wt.% PC and 20 wt.% ZIF-8 approached Robeson’s upper bound for the CO 2 /N 2 separation trade-off. These results highlight that the synergistic interplay among PU’s hard/soft segments, PC blending, and ZIF-8 nanoparticle incorporation yields membranes with significantly enhanced CO 2 separation efficiency, underscoring the potential of ternary PU/PC/ZIF-8 MMMs for advanced gas separation applications.