Synthesis of three-dimensional covalent organic frameworks through a symmetry reduction strategy.

Three-dimensional (3D) covalent organic frameworks (COFs) hold significant promise for a variety of applications. However, conventional design approaches using regular building blocks limit the structural diversity of 3D COFs. Here we design and synthesize two 3D COFs, designated as JUC-644 and JUC-645, through a methodology that relies on using eight-connected building blocks with reduced symmetry. Their structures are solved using continuous rotation electron diffraction and high-resolution transmission electron microscopy, which reveal a unique linkage with a double chain structure, a rare phenomenon in COFs. We deconstruct these structures into [4 + 3(+ 2)]-c nets, which leads to six different topologies. Furthermore, JUC-644 demonstrates high adsorption capacity for CH and n-CH (11.28 and 10.45 mmol g at 298 K and 1 bar, respectively), surpassing most known porous materials, with notable selectivity for CH/CH and n-CH/CH. This approach opens avenues for designing intricate architectures and shows the potential of COFs in CH recovery from natural gas liquids.