Synthesis of crystallinity covalent organic framework and its ratiometric fluorescent detection of trace water

The sensitive and accurate detection of trace water in solid food products is of great significance for the protection of their stability and quality. Herein, a novel crystalline COF TAPT-BPTA with fluorescence was prepared via Schiff-base condensation reaction between 4,4′,4″-(1,3,5-Triazine-2,4,6-triyl)trianiline (TAPT) and 2,5-bis(2-propyn-1-yloxy)-1,4-benzenedicarboxaldehyde (BPTA). The fluorescence of TAPT-BPTA was sensitive to trace water and can be quenched due to the disruption of intermolecular charge transfer (ICT) process by water molecules. Hence, COF TAPT-BPTA was successfully applied for sensing of trace water in common organic solvents including acetone, acetonitrile, THF and DMF with rapid response (less than 3 s) and good sensing ranges (0.05–20 v/v% for acetone, 0.10–25 v/v% for THF, 0.05–15 v/v% for ACN, and 0.05–10 v/v% for DMF). The limit of detection of water in acetone, ACN, DMF, THF were 0.0585%, 0.0631%, 0.0185% and 0.0718% (v/v), respectively. Additionally, using TAPT-BPTA as signal probe and tris(2,2′-bipyridyl)ruthenium (II) dichloride with red fluorescent as reference, a ratiometric fluorescent sensor was prepared and successfully used for the sensing of trace water in milk powder samples.