Construction of high-selectivity antifouling nanofiltration membranes through layer-by-layer assembly and in-situ fabrication of ZIF-8

LbL-confined in situ ZIF-8 growth enabled high-performance NF membranes. • ZIF-8 nanochannels improved ion sieving and transport regulation. • The membrane achieved 98.5% Na 2 SO 4 rejection with improved permeance. • The membrane achieved 93.8% flux recovery and excellent operational stability. In this study, a high-performance nanofiltration membrane was developed by integrating layer-by-layer (LbL) polyelectrolyte assembly with confined in situ growth of zeolitic imidazolate framework-8 (ZIF-8). A PEI/PSS multilayer was constructed on a polyethersulfone (PES) support through sequential electrostatic deposition, providing a nanoscale confined environment for regulating ZIF-8 nucleation and growth. Zn 2+ ions and 2-methylimidazole were subsequently introduced into the multilayer structure, enabling the formation of ZIF-8 nanocrystals within the polyelectrolyte matrix rather than conventional particle incorporation. The optimized membrane achieved a Na 2 SO 4 rejection of 98.5 ± 0.3% with a permeance of 7.1 ± 0.1 L m −2  h −1  bar −1 , representing a 65% enhancement compared with the PEI/PSS counterpart. Meanwhile, MgCl 2 rejection increased from 64.6% to 93.0%, indicating improved divalent ion selectivity. These improvements were attributed to the confined ZIF-8 nanostructures, which optimized the selective layer architecture, reduced non-selective defects, and regulated ion transport behavior. Furthermore, the membrane maintained high salt rejection (>93%) under Na 2 SO 4 concentrations of 1–5 g L −1 and exhibited excellent antifouling performance with a flux recovery ratio of 93.8 ± 0.8%. This work provides an aqueous-phase strategy for constructing MOF-polyelectrolyte hybrid selective layers with enhanced ion selectivity, antifouling capability, and operational stability for advanced water separation applications. Download: Download high-res image (92KB) Download: Download full-size image