A comprehensive review of recent developments and challenges for gas separation membranes based on two-dimensional materials

Two-dimensional (2D) materials, including graphene, have emerged as essential building nanoscale blocks for the development of high-performance membranes. At present, the gas separation membrane market is primarily dominated by polymer membranes. Part of the reason for this is the low production cost, high gas flux, and mechanical flexibility associated with polymer membranes. However, polymer membranes often exhibit relatively short lifespans, low thermal and chemical stability, and low selectivity. In contrast, 2D materials are easily modifiable, functionalizable, and amenable to composite with other materials. This makes them possess better mechanical stability, thermal stability, and higher selectivity. The atom-scale thickness of nanosheets can help to minimize transport resistance and permeation flux. Furthermore, these nanomaterials can form sub-nanometer sieving channels for precise molecular separations, particularly in gas separation applications. Notably, 2D gas separation membranes offer significant advantages over traditional membranes in terms of both permeability and selectivity. However, several challenges hinder the widespread utilization of 2D gas separation membranes. These challenges include the mechanical and long-term stability of membranes under harsh working conditions, difficulties in scalability and the high fabrication costs associated with their production. In this article, we review recent developments of composite membranes containing 2D materials to provide perspective on their application as gas separation membranes. We also provide a critical comparison of different materials for gas separation applications. This paper summarizes the current state of the art of 2D gas separation membranes, including porous graphene, GO, 2D MXene, 2D MOFs, and graphitic carbon nitride. Additionally, it describes their specific applications in CO2 capture and separation, H2 separation and purification, and helium extraction from natural gas. Furthermore, the current challenges and future development prospects of 2D material gas separation membranes are discussed.