Yin Hua-Qing, Yin Fangfei, Yin Xue-Bo
State Key Laboratory of Medicinal Chemical Biology , Tianjin Key Laboratory of Biosensing and Molecular Recognition , College of Chemistry , Nankai University , Tianjin 300071 , P. R. China.
Chem Sci. 2019 Oct 16;10(48):11103-11109. doi: 10.1039/c9sc03040a. eCollection 2019 Dec 28.
Here we reveal the effects of hydrogen bonds and alkyl groups on the structure and emission of covalent organic frameworks (COFs). Hydrogen bonds improve molecular rigidity leading to high crystallinity and restrict intramolecular rotation to enhance the emission of COFs. An excited-state intramolecular proton transfer (ESIPT) effect for dual emission is achieved the intramolecular hydrogen bonds between hydroxyl groups and imine bonds. Alkyl groups increase interlayer spacing as a natural "scaffold" and achieve a staggered AB stacking mode to decrease aggregation-caused quenching. Based on the above guidance, COF-4-OH with strong emission is prepared with 2,4,6-triformylphloroglucinol (TFP) and 9,9-dibutyl-2,7-diaminofluorene (DDAF). Strong dual emission is observed and used to differentiate organic solvents with different polarities, to determine the water content in organic solvents, and to detect different pH levels. Our work serves as a guide for the rational design of functional monomers for the preparation of emissive COFs.
在此，我们揭示了氢键和烷基对共价有机框架（COF）结构和发光的影响。氢键提高分子刚性，导致高结晶度，并限制分子内旋转以增强COF的发光。通过羟基与亚胺键之间的分子内氢键实现了双发射的激发态分子内质子转移（ESIPT）效应。烷基作为天然的“支架”增加层间距，并实现交错的AB堆积模式以减少聚集诱导猝灭。基于上述指导，使用2,4,6-三(甲酰基)间苯三酚（TFP）和9,9-二丁基-2,7-二氨基芴（DDAF）制备了具有强发光的COF-4-OH。观察到强双发射，并用于区分不同极性的有机溶剂、测定有机溶剂中的水含量以及检测不同的pH水平。我们的工作为合理设计用于制备发光COF的功能单体提供了指导。
