This review summarizes the major advances since 2012 in highly permeable and CO₂-selective polymer-based membrane materials.

This review highlights the construction and regulation of two-dimensional nanochannel membranes (2DNCMs) as well as their applications in molecular and ionic separations.

Composite membranes comprising a continuous polymer phase and a dispersed filler phase have revealed appealing potential in selective transport of molecules and ions. The multiphase characteristics of composite membranes provide more degrees of freedom to manipulate multiple interactions, tailor multiscale structures, and integrate multiple functionalities, compared to pristine polymer membranes. In this feature article, we have reviewed the various methods for the fabrication of composite membranes. In particular, we have thoroughly discussed two typical methods: the physical blending method and the sol–gel method. For each method, the major advances and challenges have been summarized. We have also tentatively delineated the new generation of composite membranes.

In nature, the biological membrane can selectively transport essential small molecules/ions through facilitated diffusion via carrier proteins. Intrigued by this phenomenon and principle, membrane researchers have successfully employed synthetic carriers and carrier-mediated reversible reactions to enhance the separation performance of synthetic membranes. However, the existing facilitated transport membranes as well as the relevant facilitated transport theories have scarcely been comprehensively reviewed in the literature. This tutorial review primarily covers the two aspects of facilitated transport theories: carrier-mediated transport mechanisms and facilitated transport chemistries, including the design and fabrication of facilitated transport membranes. The applications of facilitated transport membranes in energy-intensive membrane processes (gas separation, pervaporation, and proton exchange membrane fuel cells) have also been discussed. Hopefully, this review will provide guidelines for the future research and development of facilitated transport membranes with high energy efficiency.