by Qiuyu Lu, Yunchao Ma, Hui Li, Xinyu Guan, Yusran Yusran, Ming Xue, Qianrong Fang, Yushan Yan, Shilun Qiu and Valentin Valtchev
in Angewandte Chemie
doi : http://doi.org/10.1002/anie.201712246
Chemical functionalization of covalent organic frameworks (COFs) is critical for tuning their properties and broadening their potential applications. However, the introduction of functional groups, especially to three-dimensional (3D) COFs, still remains largely unexplored. Reported here is a general strategy for generating a 3D carboxy-functionalized COF through postsynthetic modification of a hydroxy-functionalized COF, and for the first time exploration of the 3D carboxy-functionalized COF in the selective extraction of lanthanide ions. The obtained COF shows high crystallinity, good chemical stability, and large specific surface area. Furthermore, the carboxy-functionalized COF displays high metal loading capacities together with excellent adsorption selectivity for Nd3+ over Sr2+ and Fe3+ as confirmed by the Langmuir adsorption isotherms and ideal adsorbed solution theory (IAST) calculations. This study not only provides a strategy for versatile functionalization of 3D COFs, but also opens a way to their use in environmentally related applications.