Approximately 1 nm-sized artificial tunnels in wrinkled graphene-graphene oxide composite membranes for efficient dye/dye separation and dye desalination

Efficient separation of solutes by nanofiltration membranes (NMs) is the key to the utilization of wastewater and sustainable economic development. However, the establishment of dense and narrow-dispersed artificial tunnels in NMs remains a challenge, leading to impractical water permeability and solutes selectivity for real-world applications. In this work, we construct approximately 1 nm-sized artificial tunnels within the GO-based membranes (GOMs) to balance the water permeation and nanofiltration performances, by intercalating the three-dimensional wrinkled graphene (WG) sheets with surface functional groups manipulated. Such peculiar nanotunneled structure in the WG/GO composite membrane, at the optimized WG/GO ratio of 1:2, is revealed by the selective filtration of large-sized PEG gel particles over sub-nm-sized counterparts, leading to a selective rejection of >1 nm-sized molecules (e.g. CV, CR, and TB) over sub-nm-sized impurities (e.g. NR, MB, NaCl, and Na2SO4) with excellent mechanical stability and anti-fouling property. More importantly, the dense nanotunneled structure enables the composite membrane with an increased water flux of 65.68 L m-2h- 1 bar- 1, which is ~48 times enhanced compared to that of pure GOM. Our strategy enables the precise engineering of artificial nanotunnels within compact GOM for high-performance dye/dye separation and dye desalination applications.