Constructing a 3D Covalent Organic Framework from 2D hcb Nets through Inclined Interpenetration

Three-dimensional covalent organic frameworks (3D COFs) have been of great interest due to their inherent numerous open sites and pore confinement effect. However, it has remained challenging to build 3D frameworks via inter­digitation (also known as inclined inter­penetration) by generating an entangled network formed by multiple 2D layers inclined with respect to each other. Herein, we report the first case of constructing a 3D COF, termed COF-904, through inter­digitating 2D hcb nets, which was formed via [3+2] imine condensation reactions by the use of 1,3,5-triformyl­benzene and 2,3,5,6-tetramethyl-1,4-phenylene­diamine. The single-crystal structure of COF-904 is solved, and the locations of all non-hydrogen atoms are determined by 3D electron diffraction with a resolution up to 0.8 Å. These results not only broaden the strategy for achieving 3D COFs via inter­digitation but also demonstrate that structurally complex extended frameworks can arise from simple molecules.