Synergistic metal-MOF coordination and assisted etching enabled high-flux nanofiltration membrane for superior dye/salt separation

Efficient separation of dyes from salts in high-salinity dye wastewater remains a critical challenge, limited by the permeability–selectivity trade-off and fouling susceptibility inherent to conventional nanofiltration. Here, an innovative strategy integrating synergistic metal-MOF coordination with in-situ assisted etching is proposed to construct a defect-free, highly permeable MOF-based separation layer via a scalable one-step phase inversion process. By coordinating in-situ grown ZIF-8 in the casting solution with tannic acid (TA) introduced via the coagulation bath, a crosslinked network with a high MOF loading of up to 33 wt% is constructed. Free Zn 2+ presented in the casting solution act as dynamic repairing agents, effectively healing structural defects and enhancing membrane integrity through synergistic coordination. Simultaneously, TA etches ZIF-8 to create a hollow architecture, dramatically lowering transmembrane permeation resistance and enhancing surface hydrophilicity. The resulting membrane achieves exceptional broad-spectrum dye rejection, a remarkably high pure water flux of 127 L m −2  h −1 ·bar −1 , and outstanding dye/salt selectivity (e.g., methyl blue/Na 2 SO 4 selectivity up to 967), along with superior anti-fouling performance and operational stability. This work not only presents a feasible and scalable route to fabricating high-performance nanofiltration membranes through a “coordination-repair-etching” mechanism, but also opens new avenues for sustainable resource recovery from complex saline wastewater.