Advanced development of three-dimensional covalent organic frameworks: Valency design, functionalization, and applications

Covalent organic frameworks (COFs) are a class of porous crystalline organic materials. The dynamic chemistry of covalent bonding and the applications of COFs have made great progress already. Three-dimensional (3D) COFs have attracted much attention in recent years because of their more diverse spatial structures and interconnected pore properties. High valency and functionalization are two key strategies of 3D COFs design, including the development of building blocks, topology, linkage and post synthetic modification strategy. As a result, the diversity of COF spatial structures is significantly extending and various applications in energy, environment, biology and chemical catalysis are developing. In this review, we summarized the recent articles about 3D COFs in the field of framework design, function development and applications, and put forward the critical strategies and comment, the future perspectives of the field are also prospected.