Interfacial self-organization of large-area mixed-dimensional polyamide membranes for rapid aqueous nanofiltration

Mixed-dimensional membranes are promising candidates for efficient water purification. Integrating a conventional flat two-dimensional (2D) membrane with structures of different dimensionalities is expected to create additional water transport sites. However, organizing the membrane building blocks into a mixed-dimensional hierarchy capable of facilitating rapid water transfer, while also enabling large-scale, cost-effective manufacturing, remains a significant challenge. Here we report the discovery of rapid self-organization of large-area mixed-dimensional polyamide membranes with an intriguing hierarchical structure consisting of one-dimensional nanotubes on a 2D nanofilm under room temperature using only two types of small molecules at an oil–water interface. The resulting architecture with one-dimensional nanotubes on a 2D nanofilm offers a substantially increased available area for water transport per projected area, enabling energy-efficient nanofiltration membranes with outstanding water–salt separation performance that well surpasses most state of the art membranes. Control experiments, coupled with molecular dynamic simulations, reveal that the two types of molecular monomers self-organize into a 2D nanopore network during the incipient reaction stage and then capillarity within these nanopores drives the upwards polymerization of these nanotubes. Our findings provide valuable insights into how the interplay of interfacial physical and chemical interactions organizes molecular seeds into large-scale, complex hierarchical nanostructures under ambient conditions. This opens new opportunities for developing scalable, mixed-dimensional water purification membranes. Polyamide membranes with a hierarchical structure consisting of one-dimensional nanotubes on a two-dimensional nanofilm can deliver energy-efficient nanofiltration with outstanding water–ion separation performance. This architecture provides a promising approach to the synthesis of scalable and efficient mixed-dimensional water purification membranes.