3D nanoporous crystals enabled 2D channels in graphene membrane with enhanced water purification performance

Two-dimensional (2D) materials have been received increasing attention in various fields such as physics, material science, chemistry and engineering. In particular, the graphene-based membrane is an emerging subject mainly due to the atomic thickness, simple processing and the compatibility with other materials. In the case of water treatment, stable graphene-based laminar structures as well as high separation performance are pursued. In this work, nanoporous crystals embedded graphene laminate membranes was reported for water purification. Reduced graphene oxide (rGO) nanosheets obtained from a solution chemical process act as building blocks to construct the 2D channels through a pressure-driven filtration process. By incorporating three-dimensional (3D) nanoporous crystals with sub-nano sized aperture size into the 2D graphene laminates, both the inter-layer spacing and numbers of nanofluidic channels are increased, leading to greatly-enhanced water separation performance. The optimized 3D/2D membranes exhibit 15 times higher water permeability than that of the rGO membrane with similar high dye retention rate. The significance of such 3D nanoporous structure and transport mechanism through the 3D/2D membranes is systematically studied. This general approach of enhancing the molecular transport through 2D nanofluidic channels proposed here may also find application in gas separation and battery membranes.