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