Nanofibrous Polyacrylonitrile\nMembranes Coated with\nNanosheets of Zn-Tetrakis(4-Carboxyphenyl) Porphyrin for Enhanced\nPressure Resistance and Dye/Salt Separation

Two-dimensional metal–organic framework (MOF)\nnanosheets\nhave been utilized to fabricate loose nanofiltration membranes, capitalizing\non their unique lamellar structure and regular nanopores, which facilitate\nultrafast and efficient separations. However, the structural stability\nof current MOF nanosheet membranes remains suboptimal due to the weak\ninterlayer bonding between nanosheets when a single vacuum-assisted\ndeposition method is employed. To overcome this challenge, poly(vinyl\nalcohol) (PVA) and glutaraldehyde (GA) were introduced as cross-linking\nagents in the vacuum-assisted deposition of zinc(II)-tetrakis(4-carboxy-phenyl)\nporphyrin) (ZnTCPP) nanosheets onto electrospun polyacrylonitrile\n(PAN) nanofibrous supports. The chemical bonding between nanosheets,\nPVA and GA, contributed to the superior mechanical performance of\nthe ZnTCPP-PVA-GA/PAN thin-film nanofibrous composite (TFNC) membrane,\nexhibiting an elongation at break of 62.4%, surpassing that of commercial\nnanofiltration counterparts by 2.6 times while maintaining a comparable\ntensile strength of 21.3 MPa. Furthermore, the optimized TFNC demonstrated\na high permeance of 49.5 L m<sup>–2</sup> h<sup>–1</sup> bar<sup>–1</sup> and a retention rate of 99.0% for Congo\nRed (CR) when separating CR from a mixture with NaCl, achieving a\nCR/NaCl separation factor of 92.9. Simultaneously, this membrane presented\nexcellent compression resistance and was capable of withstanding pressure\nup to 8 bar without compromising separation performance.