Graphene oxide laminates intercalated with 2D covalent-organic frameworks as a robust nanofiltration membrane

The separation performances of laminate membranes made of two-dimensional (2D) materials depend heavily on their nanoscale structures. Apart from tuning the interlayer spacings of 2D materials, the pore sizes of supporting substrates also influence membrane performances significantly. Herein, we intercalated a rigid 2D covalent-organic framework (COF) into partially reduced graphene oxide (prGO) laminates to realize robust prGO/COF laminate membranes. On the one hand, the atomically thin 2D COF with pores serves as a nanospacer to increase the interlayer spacing between prGO nanosheets and provide direct transfer channels, reducing water transfer resistance. On the other side, the COF enhances the self-supporting capacity of prGO networks on a substrate with large pores. Our model calculation reveals a 53.4% increase in the effective membrane surface area, driven by reinforced wrinkles and corrugations. This strategy leads to 27 times increase in the water permeance of the optimized prGO/COF laminate membrane compared to the pristine prGO membrane without sacrificing its rejection rates to organic dyes. Furthermore, the prGO/COF membranes can withstand a great extent of deformation under 5 bar for 10 h in nanofiltration tests. Overall, this work provides a multi-directional strategy and a design principal guidance to realize high-performance and robust 2D material-based laminate membranes for various potential applications.