The Strategies of Improving Chemical Stability of Imine-Linked Covalent Organic Frameworks.

Imine-linked covalent organic frameworks (COFs) have wide applications in molecular separation, gas storage, photocatalysis, electrocatalysis, energy storage, and optoelectronic devices because of their unique advantages such as good crystallinity, permanent porosity, and tunable pore structure. However, the practical applications of imine-linked COFs in chemical catalysis and gas separation may be hindered due to their reduced chemical stability in acidic or basic conditions. Recently, various effective strategies have been developed to improve chemical stability of imine-linked COFs. In this review, we summarize the important advances in improving the stability of imine-linked COFs from the viewpoint of design strategies, including electron-donating group substitution, steric tuning, fluorine substitution, redox conversion, six-membered cyclization, five-membered cyclization, and so on. Moreover, the challenges and perspectives are also described to promote the realization of stable imine-linked COFs, which will meet the requirements of these materials in practical applications.