Bika Panagiota, Ioannidis Nikolaos, Gatou Maria-Anna, Sanakis Yiannis, Dallas Panagiotis
Institute of Nanoscience and Nanotechnology, National Centre for Scientific Research, 15341 Athens, Greece.
Laboratory of General Chemistry, School of Chemical Engineering, National Technical University of Athens, Zografou Campus 9, Iroon Polytechniou Str., GR-15780 Zografou, Athens, Greece.
Langmuir. 2022 Mar 15;38(10):3082-3089. doi: 10.1021/acs.langmuir.1c02910. Epub 2022 Mar 3.
In this work, we reveal the coordination of copper ions absorbed by a series of covalent organic frameworks. The frameworks were synthesized through the nucleophilic substitution of either cyanuric chloride or phosphonitrilic chloride trimer by 4,4'-bipyridine, and they were utilized as absorbers for the removal of copper ions from aqueous solutions. The exfoliated counterpart of the layered network was compared to the bulk materials in terms of the copper retention capacity and efficiency. The ion absorption capacity of copper ranged from 100 to 290 mg/g depending on the morphology and chemical structure of the framework. As evidenced by the SEM and XRD analysis, the copper absorption induced certain morphological changes in the networks. EPR spectroscopy revealed the key finding of this study: the trigonal bipyramidal configuration of the copper ions in their divalent state, coordinated with the nitrogen of the core units, 4,4'-bipyridine, and chlorine ions. The analysis of the thoroughgoing experiments bridges the gap between coordination molecular chemistry and the field of covalent organic frameworks. EPR explores how the unique trigonal bipyramidal coordination could be suppressed in the end by the environment and, more specifically, by the addition of glycerol to the aqueous dispersions of the covalent organic frameworks.
在这项工作中，我们揭示了一系列共价有机框架吸收铜离子的配位情况。这些框架是通过三聚氯氰或三聚磷腈与4,4'-联吡啶的亲核取代反应合成的，并用作从水溶液中去除铜离子的吸收剂。将层状网络的剥离对应物与块状材料在铜保留容量和效率方面进行了比较。根据框架的形态和化学结构，铜的离子吸收容量在100至290 mg/g之间。扫描电子显微镜（SEM）和X射线衍射（XRD）分析表明，铜的吸收在网络中引起了一定的形态变化。电子顺磁共振（EPR）光谱揭示了本研究的关键发现：二价态铜离子的三角双锥构型，与核心单元4,4'-联吡啶的氮原子和氯离子配位。深入实验的分析弥合了配位分子化学与共价有机框架领域之间的差距。EPR探索了最终环境，更具体地说是通过向共价有机框架的水分散体中添加甘油，如何抑制独特的三角双锥配位。
