Leaf-veins-inspired nickel phosphate nanotubes-reduced graphene oxide composite membranes for ultrafast organic solvent nanofiltration

Organic solvent nanofiltration (OSN) membranes provide extraordinary opportunities for environment friendly and cost-competitive solvent recovery in petrochemical and pharmaceutical purifications. Currently, membranes that based on two-dimensional (2D) materials are extremely attractive in ultrafast molecular separations owing to the atomic thickness and remarkable physicochemical properties of the 2D nanosheets. Inspired by the structures and functions of vessel element that transport water in leaf veins, nickel phosphate nanotubes-reduced graphene oxide (NPTs-rGO) ultrathin laminar membrane is successfully prepared for ultrafast organic solvent nanofiltration. The in-situ synthetic NPTs can not only contribute to the size-dependent ultrafast molecular separation of the rGO membrane by providing additional molecular transport pathways as well as enlarging the interlayer space of the rGO layer, but also enhance the stability of the resultant membrane. The optimum membrane exhibits a methanol permeance of 670 L m⁻² h⁻¹ bar⁻¹ and a high rejection toward molecules greater than 2 nm (MWCO: 650 Da). More importantly, the NPTs-rGO membrane shows promising anti-swelling property under OSN operating conditions. Inspired by leaf veins, this strategy provides insight into designing high-performance lamellar membranes with tubular-channel network, which may promote the fabrication and application of lamellar membranes in OSN.