Ultraselective polyamide nanofiltration membranes inspired by squid skin biomimicry

Highly selective nanofiltration membranes are ideal candidates for efficient water purification. However, achieving superior selectivity without sacrificing water permeance remains a considerable challenge. Drawing inspiration from the structural features of squid skin, a biomimetic strategy was devised that integrates cyclohexane-induced swelling with surface grafting employing hydrophilicity-tuned monomers to enhance the performance of polyamide thin-film composite membranes (PA-TFC). Remarkably, grafting with aminoacetaldehyde dimethyl acetal (ADA), the most hydrophilic monomer, effectively mimicked the natural hydration layer, thereby enabling rapid and unhindered water transport. Consequently, the resulting ADA-modified nanofiltration (ADA-NF) membrane exhibits an ultrahigh NaCl/Na 2 SO 4 separation factor of 263.2, while doubling the water permeance to 15.9 L m −2  h −1  bar −1 . Additionally, large-scale roll-to-roll production of this type of biomimetic nanofiltration membrane has been successfully demonstrated. The ADA-NF membrane exhibits significantly enhanced anti-fouling properties due to its tailored surface charges, while maintaining stable performance. The ADA-NF membrane offers a practical route to address the permeance-selectivity trade-off, while its fabrication strategy maintains a high degree of compatibility with existing industrial production lines. This unique biomimetic strategy provides valuable insights into the rational design of NF membranes for highly selective separation.