High-Performance Turn-On Fluorescent Metal–Organic Framework for Detecting Trace Water in Organic Solvents Based on the Excited-State Intramolecular Proton Transfer Mechanism

Simple, fast, and sensitive detection of trace water
in organic
solvents is an urgent requirement for chemical industries. Herein,
combining the unusual excited-state intramolecular proton transfer
(ESIPT) mechanism with the effective strategy of pore space partition,
for the first time, we construct a powerful fluorescent metal–organic
framework (SNNU-301) probe with excellent water stability. The SNNU-301
probe shows a remarkable performance for turn-on ESIPT-based fluorescence
response to water in nine common organic solvents, exhibiting wide
linear ranges, low limit of detection values, and ultrafast response,
especially in dimethyl sulfoxide (0–5.2%; 0.011%, v/v; 110
s). The typical ESIPT-sensitive linker 2,5-dihydroxyterephthalate
(DHBDC) imparts it with discriminative detection properties via enol–keto
tautomerism, and light-responsive triangular tri(pyridin-4-yl)-amine
(TPA) realizes pore space partition. The theoretical calculation gives
an in-depth explanation about the proton transfer mechanism. Comparative
experiments and GCMC simulation provide evidence that the synergy
of the ESIPT process and TPA of the framework further boosts its performance
effectively. Definitely, this work not only offers a promising candidate
with fast detection speed, high sensitivity, excellent universality,
and visual observation for the determination of water in organic solvents
but also provides valuable guidance for the design of high-performance
fluorescent probes.