The latest progress of covalent organic framework (COF) membranes is summarized. The concept of pore chemistry is introduced and various strategies are proposed for engineering of pore structures to improve gas separation of COF membranes. Typical gas separations are showcased for COF membranes. The future for COF membrane and gas separation is highlighted.

Abstract

Covalent organic frameworks (COFs) have been widely used in gas separation due to their permanent open porosity, highly ordered crystalline structures and excellent processability. The pore structure of a membrane determines its performance in gas separation. This review highlights the importance of pore chemistry in COF membranes with gas-separation function. The latest advancements of various strategies are presented to regulate the pore structures of COF membranes, which are clearly illustrated by the representative examples. The application of gas separation by COF membranes is reviewed. The separation mechanisms are systematically summarized, with a focus on correlating the structure (pore size, wall, and dimensionality) and the performance (gas permeability and selectivity). The future challenges and prospective of COF membranes in the field of gas separation are briefly described, aiming to provide guidance for the potential development of next-generation membrane in the gas separation field.