Topological Isomerism in Three-Dimensional Covalent Organic Frameworks
Yaozu Liu, Jingwei Li, Jia Lv, Zitao Wang, Jinquan Suo, Junxia Ren, Jianchuan Liu, Dong Liu, Yujie Wang, Valentin Valtchev, Shilun Qiu, Daliang Zhang, Qianrong Fang
Abstract
Although isomerism is a typical and significant phenomenon in organic chemistry, it is rarely found in covalent organic framework (COF) materials. Herein, for the first time, we report a controllable synthesis of topological isomers in three-dimensional COFs via a distinctive tetrahedral building unit under different solvents. Based on this strategy, both isomers with a dia or qtz net (termed JUC-620 and JUC-621) have been obtained, and their structures are determined by combining powder X-ray diffraction and transmission electron microscopy. Remarkably, these architectures show a distinct difference in their porous features; for example, JUC-621 with a qtz net exhibits permanent mesopores (up to ∼23 Å) and high surface area (∼2060 m 2 g –1 ), which far surpasses those of JUC-620 with a dia net (pore size of ∼12 Å and surface area of 980 m 2 g –1 ). Furthermore, mesoporous JUC-621 can remove dye molecules efficiently and achieves excellent iodine adsorption (up to 6.7 g g –1 ), which is 2.3 times that of microporous JUC-620 (∼2.9 g g –1 ). This work thus provides a new way for constructing COF isomers and promotes structural diversity and promising applications of COF materials.