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Observation of Interpenetration Isomerism in Covalent Organic Frameworks

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journal contribution
posted on 21.05.2018, 00:00 by Tianqiong Ma, Jian Li, Jing Niu, Lei Zhang, Ahmed S. Etman, Cong Lin, Dier Shi, Pohua Chen, Li-Hua Li, Xin Du, Junliang Sun, Wei Wang
We report herein the first example of interpenetration isomerism in covalent organic frameworks (COFs). As a well-known three-dimensional (3D) COF, COF-300 was synthesized and characterized by the Yaghi group in 2009 as a 5-fold interpenetrated diamond structure (dia-c5 topology). We found that adding an aging process prior to the reported synthetic procedure afforded the formation of an interpenetration isomer, dia-c7 COF-300. The 7-fold interpenetrated diamond structure of this new isomer was identified by powder X-ray diffraction and rotation electron diffraction analyses. Furthermore, we proposed a universal formula to accurately determine the number of interpenetration degrees of dia-based COFs from only the unit cell parameters and the length of the organic linker. This work not only provides a novel example to the category of interpenetration isomerism but also provides new insights for the further development of 3D COFs.