Construction of metal-organophosphate (MOPMs) interlayers for preparing high-performance polyamide composite nanofiltration membranes

Achieving an ideal balance between water permeance and separation selectivity remains a significant bottleneck in advancing nanofiltration membrane for dye/salt separation. This work reports the use of metal–organic phosphate membranes (MOPMs) as an interlayer to regulate the retention and diffusion of piperazine (PIP) monomers on the substrate, thereby optimizing the thickness and bacteriostasis properties of the polyamide layer. Under optimal modification conditions with 0.2 mg/mL PA, the water permeance of the MOPMs-0.2-IP considerably elevated to 42.18 L m⁻²h⁻¹bar⁻¹, approximately double that of the controlled membrane, while maintaining comparable dye/salt separation performance (Congo red >99.9 %, NaCl: 18.7 %, MgCl₂: 12.4 %). Noticeably, compared with existing nanofiltration membranes, MOPMs-0.2-IP exhibits excellent permeability and separation capabilities. This work provides valuable insights into optimizing polyamide layers through the use of intermediate layers, advancing the development of high-performance nanofiltration membranes.