Two-dimensional materials: an emerging platform for gas separation membranes

Graphene and its derivatives are of particular interest as emerging platforms for molecular separation. However, there are abundant 2D nanomaterials other than graphene that have unique and intriguing structural features that can be exploited for membrane-based separation that have not been extensively studied. Furthermore, from a materials synthesis standpoint, realizing high yield and scalable methods for massive production of 2D nanomaterials is critical. Liquid-based exfoliation to produce 2D nanosheets from layered bulk crystals has recently drawn considerable attention. Such single-layered or few-layered 2D nanosheets can be formed into laminate membranes with exceptional molecular-sieving properties or more preferably utilized as high aspect ratio nanofillers to improve the separation performance of polymer membranes. Most remarkably, 2D nanosheets can mitigate the well-known plasticization phenomenon in polymer membranes by interacting strongly with the polymer chains. There is no doubt that these emerging 2D nanomaterials will facilitate fabrication of next-generation membranes.