Li Zhongping, Huang Ning, Lee Ka Hung, Feng Yu, Tao Shanshan, Jiang Qiuhong, Nagao Yuki, Irle Stephan, Jiang Donglin
Department of Chemistry, Faculty of Science , National University of Singapore , 3 Science Drive 3, Singapore 117543 , Singapore.
Area of Materials Chemistry, School of Materials Science , Japan Advanced Institute of Science and Technology , 1-1 Asahidai, Nomi 923-1292 , Japan.
J Am Chem Soc. 2018 Oct 3;140(39):12374-12377. doi: 10.1021/jacs.8b08380. Epub 2018 Sep 20.
Covalent organic frameworks (COFs) offer ordered π structures that are useful for developing light-emitting materials. However, most COFs are weak in luminescence. Here we report the conversion of less emissive COFs into light-emitting materials via a pinpoint surgery on the pore walls. Deprotonation of the N-H bond to form an anionic nitrogen species in the hydrazone linkage can eliminate the nitrogen-related fluorescence quenching pathway. The resulting COF enhances the fluorescence in a linear proportion to the progress of deprotonation, achieving a 3.8-fold improved emission. This pinpoint N-H cleavage on the pore walls can be driven only by the fluoride anion while other halogen anions, including chloride, bromide, and iodide, remain inactive, enabling the selective fluorescence switch-on sensing of the fluoride anion at a ppb level.
共价有机框架（COFs）提供了有序的π结构，这对于开发发光材料很有用。然而，大多数COFs的发光较弱。在此，我们报告了通过对孔壁进行精确手术将发光较弱的COFs转化为发光材料的方法。腙键中N-H键去质子化形成阴离子氮物种可以消除与氮相关的荧光猝灭途径。所得的COF荧光增强与去质子化进程呈线性比例，发射提高了3.8倍。这种孔壁上的精确N-H裂解仅由氟阴离子驱动，而其他卤素阴离子，包括氯离子、溴离子和碘离子，则无活性，从而能够在ppb水平上对氟阴离子进行选择性荧光开启传感。
