Root-like polyamide membranes with fast water transport for high-performance nanofiltration

Abstract

Synthetic membranes universally exhibit a pernicious trade-off effect, on which there exists an upper bound between permeability and selectivity. Tremendous efforts are made to design crumpled membranes to further break through the bottleneck. In this work, we proposed that a nano-pleated membrane surface with ridged nanostructures enables rapid transport of water molecules. Here, a root-like, ultrathin thin film composite (TFC) membrane was carefully designed via incorporation of a sacrificial ZIF-L layer into a polyamide layer, followed by its removal in a weak acid solution. The best performing membranes displayed ultrahigh water permeances of 48.9 L m⁻² h⁻¹ bar⁻¹ with a comparable rejection of sodium sulfate, surpassing the upper limit of conventional desalting membranes. The utilization of sacrificial ZIF-L templates in the regulation of the nanofilm morphology is suggested to be promising for fabrication of highly permeable NF membranes.