A "turn-on" fluorescent sensor based on three-component covalent organic framework for trace water detection.

[Display omitted] • Five COFs with aggregation-induced emission characteristics were synthesized. • The response sensitivity was adjusted by adjusting the component ratio. • The first COF based fluorescence sensor for ultra-trace water detection. • Test strips were prepared for visual detection of trace water in the field. Trace amount of H 2 O is difficult to eliminate in laboratory environments and chemical industries as impurities. In some chemical reactions, trace amount of H 2 O can alter final reaction products, yield, and selectivity. So, the detection of trace H 2 O is very important. Herein, a series of TFPT [X] -BMTH- covalent organic frameworks (COFs) (X = 0, 33, 50, 67, 100 %) with intramolecular charge transfer effect (ICT) and aggregate-induced emission (AIE) characteristics were synthesized by amino-aldehyde condensation reaction between 2,5-bis(2-methoxyethoxy)terephthalohydrazide (BMTH)/ 1,3,5-tris(p-formylphenyl)benzene (TFPB) and 4,4′,4′'-(1,3,5-triazine-2,4,6-triyl)tribenzaldehyde (TFPT). By changing TFPT' content in TFPT [X] -BMTH-COFs, the ICT and AIE of TFPT [X] -BMTH-COFs can be controlled, and accordingly the response to trace H 2 O can be adjusted. A H 2 O sensor based on TFPT [67] -BMTH-COF with a wide linear range from 0 wt% to 0.5 wt% was developed and the detection limit was 0.00007 wt%. In addition, a portable fluorescent test paper based on TFPT [67] -BMTH-COF for visual detection of trace H 2 O in honey samples and salt was constructed. This work has important guiding significance for the development of fluorescent probes for the visual detection of trace water. [ABSTRACT FROM AUTHOR]