Covalent organic framework membranes for CO2 separation: recent advances and challenges

Global carbon dioxide (CO₂) emissions caused by the massive utilization of fossil fuels continue to rise, exacerbating the greenhouse effect. Membrane-based CO₂ separation processes are a promising technology for carbon reduction. Covalent organic framework (COF) membranes have shown great potential in the field of gas separation due to their high porosity, tunable pore size, and chemical stability. Utilizing the advantages of COFs to prepare gas separation membranes has become a current research hotspot. This review analyzes and summarizes the great advances in and challenges associated with the synthetic methods of COFs and COF membranes for CO₂ separation. Furthermore, the optimizing strategies for the construction of high-performance COF membranes for CO₂ separation were systematically summarized in terms of defect engineering, ionic liquid (IL) modification, post-modification, pore structure modulation, and inter-material synergy. And the specific applications of COF membranes in CO₂ separation and the corresponding separation mechanisms were comprehensively introduced. Finally, we give our personal insights into the challenges and opportunities for the future research on COF membranes for the CO₂ separation. It is expected that this review will enable scholars to grasp the recent progress in COF membranes for CO₂ separation in a timely manner and hence provide some valuable insights into the future investigations to accomplish further improvements.