(399p) Nanoporous Crystals Channeled Two-Dimensional-Material Membranes with Highly-Enhanced Water Purification Performance

Two-dimensional (2D) materials have been received increasing attention in various fields such as physics, material science, chemistry and engineering. The unique feature of atomic thickness enables 2D materials to develop high-performance separation membranes with maximum permeate flux because of the minimum membrane thickness that can be achieved. As a representative class of 2D materials, graphene-based materials have been used to fabricate membranes for selectively transporting water, ions and gases. In particular, graphene oxide (GO) membranes show great potential in water purification and gas separation due to the facile processing property and versatile functionality of GO. While for practical implementation, the productivity and stability of current GO membranes for water purification still need to be improved. Intercalation and crosslinking approaches were employed to address the challenges, however, selectivity and flux were often reduced, respectively.

In this work, we report nanoporous crystals embedded graphene laminate membranes 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 the 3D nanoporous crystals with sub-nano sized aperture size (e.g., UiO-66, Prussian blue) into the 2D graphene laminates, both the inter-layer spacing and numbers of nanofluidic channels are increased, leading to a highly-enhanced water transport property. The optimized 3D/2D membranes exhibit 15 times higher water permeability (30 L m^-2 h^-1 bar^-1) than that of the rGO membrane with similar high dye rejection rate (>95% for rhodamine B). The significance of such 3D nanoporous structure and transport mechanism through the 3D/2D membranes are 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.

Acknowledgements

This work was financially supported by the National Natural Science Foundation of China (Nos. 21490580, 21476107, 21406107).