Engineering microporous organic framework membranes for CO2 separations

The soaring increase in CO2 emissions in the atmosphere is drastically changing our global climate and environment. To alleviate this threat, CO2 separation by membrane technology is evolving as an efficient strategy to control this emission. In the membrane process, membrane materials play a central role. Microporous materials have attracted much attention, particularly for the considerable effort in the recently developed porous organic frameworks (POFs). POFs have a promising potential in membrane applications for CO2 separation owing to the intrinsic advantages of high porosity and good processability. This review summarizes the latest advances in the development of POF membranes for CO2 separations from diverse sources. Special attention is focused on effective approaches to engineer the properties of POF membranes in terms of topological design, chemical functionalization and mixed-matrix technique, in order to enhance CO2 separation performance. The relationship between POF structures and CO2 permeability (selectivity) is also highlighted. Representative examples of POF membranes for CO2 separations from flue gas, natural gas or syngas are incorporated. A brief perspective on the future research directions in this rapidly growing field is also given.