Mixed matrix membranes constructed from electrospun nanofiber backbones with orientationally aligned MOFs for superior mechanical and H2/CO2 separation properties

In this study, a novel polyimide (PI)/metal-organic frameworks (MOFs)/polyetherimide (PEI) composite membrane was fabricated for gas separation applications. The directional alignment of MOFs on PI electrospun nanofibers was achieved by an in-situ growth method, resulting in the construction of continuous, fast, and low-resistance gas transport channels in the composite membrane (PEI/PI@ZIF-67). This PI nanofiber backbone with a three-dimensional network structure not only remarkably enhanced the interfacial compatibility between the polymer and the MOFs, but also significantly improved the mechanical strength of the membrane, resulting in a tensile strength of the composite membrane of 100 MPa. Moreover, the introduction of PI fibers promoted the oriented alignment of the MOFs and enhanced the H 2 separation performance. The H 2 permeability of PEI/PI@ZIF-67-3 was 9.5 Barrer, which was 439% higher than that of the pure PEI membrane. The H 2 /CO 2 selectivity was 9.3, which was 3.3 times higher than that of the pure PEI membrane. This can be attributed to the porous structure of ZIF-67 and the complex and tortuous gas transport path provided by the PI fibers, allowing the optimized composite design of PEI/PI@ZIF-67 to simultaneously improve gas permeability and selectivity. Furthermore, the prepared fiber composite membranes exhibited good hydrophobicity and thermal stability. Consequently, PEI/PI@ZIF-67, with its continuous and fast transport path, shows great potential for CO 2 capture and H 2 recovery applications.