Post-Synthetic Modification of a Fluorescent Covalent Organic Framework as a Multifunctional Sensor for Efficient Detection of 5-Hydroxytryptamine and Its Metabolite and Latent Fingerprint Identification

In this study, a functionalized vinyl-linked 2D fluorescent covalent organic framework (COF) (TMT-TA-COOH) is constructed by post-synthetic modification (PSM) of a TMT-TA COF, which is composed of trimethyltriazine (TMT) and terephthalaldehyde (TA). The fluorescent COF (TMT-TA) has the characteristics of good crystallization and stability, but the dispersibility in water is poor, which requires further PSM. After PSM, the obtained TMT-TA-COOH not only exhibits good dispersibility in water but also displays stronger binding ability to analytes, which presents high sensitivity for quantitative identification of 5-hydroxytryptamine (5-HT) and its metabolite 5-hydroxyindole-3-acetic acid (5-HIAA) in water. Moreover, TMT-TA-COOH can specifically recognize 5-HT in serum and 5-HIAA in urine with a fast response, good anti-interference performance, and real-time visualization, which enables the TMT-TA-COOH to be a tool for early detection of neurological diseases and biomarkers for carcinoid tumors. In addition, TMT-TA-COOH is also a good candidate for latent fingerprint (LFP) identification, which has the characteristics of high contrast and low background interference. This work not only provides a promising platform for the sensing application of fluorescent COFs in aqueous solution but also opens up a new way for the detection of LFP information.