2D Heterostructured Nanofluidic Channels for Enhanced Desalination Performance of Graphene Oxide Membranes

The two-dimensional (2D) lamellar membrane assembly technique shows substantial potential for sustainable desalination applications. However, the relatively wide and size-variable channels of 2D membranes in aqueous solution result in inferior salt rejections. Here we show the establishment of nanofluidic heterostructured channels in graphene oxide (GO) membranes by adding g-C3N4 sheets into GO interlamination. Benefiting from the presence of stable and sub-nanometer wide (0.42 nm) GO/g-C3N4 channels, the GO/g-C3N4 membrane exhibits salt rejections of ∼90% with water permeances of above 30 L h–1 m–2 bar–1, while the pure GO membrane only has salt rejections of below 30% accompanied by water permeances of below 4 L h–1 m–2 bar–1. Combining experimental and theoretical investigations, size exclusion has proved to be the dominating mechanism for high rejections, and the ultralow friction water flow along g-C3N4 sheets is responsible for permeation enhancements. Importantly, the GO/g-C3N4 membrane shows promising long-term, antioxidation, and antipressure stability.