Design and applications of three dimensional covalent organic frameworks.

Covalent organic frameworks (COFs), as an emerging class of crystalline porous polymers connected by dynamic covalent bonds, have been well studied over the past decade. Recently, three dimensional (3D) COFs have attracted extensive interest for the synthesis and applications of novel COFs. The principal reason for this rising trend is based on their unique porous features and excellent performances compared to previously reported two dimensional (2D) frameworks with the layered AA-stacking mode. This critical review describes the current state-of-the-art development of 3D COFs in the design principles, synthetic methods, functionalization strategies, and potential applications. Some major challenges associated with future perspectives are further discussed, inspiring the development of 3D COFs.