A green-emitting fluorescent covalent organic framework nanostructure for visual sensing of folic acid

• Published in: Dyes and pigments 2023-01, Vol.208, p.110878, Article 110878
• Main Authors: Wen, Qiu-Lin, Wu, Bi-Chao, Pu, Zheng-Fen, Li, Rong Sheng, Ling, Jian, Cao, Qiue
• Format: Article
• Language: English
• Subjects: Covalent organic frameworks; Fluorescence; Folic acid; Visual detection
• ISSN: 0143-7208; 1873-3743
• DOI: 10.1016/j.dyepig.2022.110878

Most solid-state imine-linked covalent organic frameworks (COFs) are non-fluorescent due to aggregation-caused quenching because of strong π-π interactions and rotationally unstable imine bonds in the stacked layers of COFs. Here, we report a green-emitting fluorescent imine-based COF (ODA-TP-COF) by integrating flexible building blocks and transforming the COF into nanoscale sheets. Due to the existence of flexible non-planar units, the interlayer distance of ODA-TP-COF increases, which weakens the π-π interaction and thus reduces the aggregation-caused fluorescence quenching. Our further study found that the ODA-TP-COF dispersed in different solvents has different fluorescence properties, and surprisingly when methanol was used as the solvent for ODA-TP-COF, the presence of a small biological molecule, folic acid, could significantly and selectively induce a blue-shifts of ODA-TP-COF fluorescence peak. It is the first time that the ODA-TP-COF could serve as a highly selective fluorescent probe for the visual detection of folic acid. [Display omitted] •Prepared a green-emitting fluorescent imine-based COF by integrating flexible building blocks.•Folic acid could significantly and selectively induce the blue-shift of the fluorescence peak of COF.•It is the first time that the COF was served as a fluorescent probe for the visual detection of folic acid.