Jin Fazheng, Wang Tonghai, Zheng Han, Lin En, Zheng Yunlong, Hao Liqin, Wang Ting, Chen Yao, Cheng Peng, Yu Kuang, Zhang Zhenjie
MOE International Joint Laboratory of Materials Microstructure, Institute for New Energy Materials and Low Carbon Technologies, School of Material Science and Engineering, Tianjin University of Technology, Tianjin 300384, China.
College of Chemistry, Nankai University, Tianjin 300071, China.
J Am Chem Soc. 2023 Mar 22;145(11):6507-6515. doi: 10.1021/jacs.3c00550. Epub 2023 Mar 12.
Developing strategies to enhance the structural robustness of covalent organic frameworks (COFs) is of great importance. Here, we rationally design and synthesize a class of cross-linked COFs (COFs), in which the two-dimensional (2D) COF layers are anchored and connected by polyethylene glycol (PEG) or alkyl chains through covalent bonds. The bottom-up fabrication of these COFs is achieved by the condensation of cross-linked aldehyde monomers and tritopic amino monomers. All the synthesized COFs possess high crystallinity and porosity, and enhanced structural robustness surpassing the typical 2D COFs, which means that they cannot be exfoliated under ultrasonication and grinding due to the cross-linking effect. Furthermore, the cross-linked patterns of PEG units are uncovered by experimental results and Monte Carlo molecular dynamics simulations. It is found that all COFs are dominated by vertical cross-layer (interlayer) connections (clearly observed in high-resolution transmission electron microscopy images), allowing them to form quasi-three-dimensional (quasi-3D) structures. This work bridges the gap between 2D COFs and 3D COFs and provides an efficient way to improve the interlayered stability of COFs.
制定增强共价有机框架（COF）结构稳健性的策略至关重要。在此，我们合理设计并合成了一类交联COF，其中二维（2D）COF层通过聚乙二醇（PEG）或烷基链通过共价键锚定并连接。这些COF的自下而上制备是通过交联醛单体和三官能氨基单体的缩合实现的。所有合成的COF都具有高结晶度和孔隙率，并且结构稳健性增强，超过了典型的2D COF，这意味着由于交联效应，它们在超声处理和研磨下不会被剥离。此外，实验结果和蒙特卡罗分子动力学模拟揭示了PEG单元的交联模式。发现所有COF都以垂直跨层（层间）连接为主（在高分辨率透射电子显微镜图像中清晰可见），使它们能够形成准三维（准3D）结构。这项工作弥合了2D COF和3D COF之间的差距，并提供了一种提高COF层间稳定性的有效方法。
