High-performance graphene oxide desalination membranes enabled by size-sieving, ion exclusion, and cation recognition mechanisms.

Graphene oxide (GO)-based membranes are promising for sustainable water purification due to their sub-nanometer interlayer channels, which provide ultrafast water transport and high salt rejection. However, they generally exhibit limited structural stability in aqueous media, leading to increased interlayer spacing and reduced salt rejection. Here, the polysaccharide chitosan (CH) is introduced into the GO galleries through a one-pot pressure-assisted self-assembly method to stabilize the GO interlayer spacing at a specific distance. Furthermore, CH, as a positively charged polysaccharide, confers the membrane with local positive charges. These, in combination with the inherent negative charges on the GO surface, result in GO-based membranes possessing simultaneous size-sieving, cation recognition, and anion exclusion capability. The ratio of CH: GO was found as a key parameter, controlling the interlayer spacing, nanochannel total charge density, and cation charge density along the channel. The results showed that the membrane containing 0.02 mg/cm