ABSTRACT
Covalent organic frameworks (COFs), represent a class of structurally ordered, an emerging family of crystalline porous polymers possessing a large surface area to volume ratio, constructed with the light atoms via covalent bonds. Because of the availability of organic units and the diversity of topologies and linkages, COFs have emerged as a new arena of organic materials. So far, over 20 kinds of linkages have been invented in constructing COFs. The contemporary synthetic strategies of COFs can be categorized into two major branches, the “monomers to COFs” and the “polymers to COFs” strategies. In recent decades, most reports were concentrated on conjugated two-dimensional (2D) sheets. In divergence, three-dimensional (3D) COFs are still not as much studied due to the less availability of appropriate molecular building units and comparatively complex structure determination. Due to flexible molecular design and synthetic strategies, high conjugated and modifiable structures, large surface area, and porosity, COFs have shown promising perspectives in energy applications including photocatalysis, electrocatalysis, supercapacitors, metal-ion/sulfur batteries, etc.
