Pore engineering in covalent organic framework membrane for gas separation

Covalent Organic Frameworks (COFs) have attracted significant interest as promising separation membrane materials for their well-organized porous system and highly ordered crystalline structure. However, compared with the molecular and ionic separation in liquid phase, the advance of the COF membrane in gas separation has been relatively slow. To achieve desirable gas separation performance, the pore size of the COF membrane is expected to be regulated into the gas molecule-selective region, and also the tuning of pore enviroment is of importance. This review focuses on the key progress of the pore regulation strategies for the COF membrane towards gas separation. We highlight the different design concepts for selective gas transport channels, and introduce the specific applications to elucidate the structure-performance relationship of the COF membrane. We discuss the critical challenges and opportunities faced by the COF membranes in the field of gas separation, aiming at guiding the direction of the future efforts and promoting their development.