Functionalization of covalent organic frameworks by metal modification: Construction, properties and applications

As emerging crystalline porous materials, covalent organic frameworks (COFs) have drawn great interest due to their tunable porosity and modifiable skeletons. Multiple applications of COFs rely on the previous chemical functionality of organic building units or posterior modification of frameworks. The metal modification strategy utilizes metal–ligand coordination reactions to incorporate metal species into COF skeletons, providing the possibility for functionalization. In this review, we discuss the pristine properties (pore design, chemical stability and scalability) and characterization techniques of COFs to fully recognize these charming materials. Particular attentions are given to the construction (theoretical simulations and actual operation synthesis methods) and metallized properties (adsorption site, binding energy and structural effect) of metal-modified COFs in view of verifying the feasibility of modification. Moreover, the applications of hybrids in gas adsorption and catalysis are presented. Finally, we summarize the challenges and give outlook in the future perspectives of this modification strategy.