Ultrathin Two-Dimensional Membrane by Assembling Graphene and MXene Nanosheets for High-performance Precise Separation

Abstract

Membrane technology has attracted great attentions in the field such as separation and purification due to its high efficiency and low energy consumption. To break the “trade-off” limitation between high permeability and selectivity, tremendous efforts have been oriented towards how to design and exploit ultrathin membranes. Graphene and MXene, which own single-atom layer thickness, large specific surface area, ease of fabrication, and controllable layer-by-layer assembly, have emerged as ideal candidates for ultrathin membranes. Compared to conventional polymeric membrane materials, 2D separation membranes assembled by graphene and MXene nanosheets, leveraging their unique laminar structure and ultrathin thickness, significantly shorten the transport path of guest molecules, minimizing mass transfer resistance while maintaining or even enhancing separation selectivity. Furthermore, precise sieving of guest molecules can be achieved through tuning the interlayer spacing or pore sizes of 2D nanosheets. This review comprehensively summarizes the state-of-the-art advancements on ultrathin 2D membranes assembled by graphene and MXene nanosheets, including the synthesis of nanosheets, the fabrication principles, structure design, and mass transfer mechanism of ultrathin 2D membranes, and related precise separation applications. We focus on advanced ultrathin 2D membranes which simultaneously exhibit high permeability and selectivity, and discuss the strategies and mechanisms that suitable to develop ultrathin 2D membrane can overcome the “trade-off” effect that inherent in traditional separation membranes. Finally, critical consideration on the opportunities and challenges of ultrathin 2D membrane assembled by graphene and MXene nanosheets towards high-performance precise separation are also presented.