Highly Stable Zn(II) Metal–Organic Framework as an “On–Off–On” Fluorescence Sensor toward H<sub>2</sub>PO<sub>4</sub><sup>–</sup> Anion in the pH-Dynamic System
Yu Li, Chen Cao, Teng‐Fei Zheng, He‐Rui Wen, Sui‐Jun Liu
Abstract
In a dynamic system, fluorescent probes with dual signals not only efficiently identify target analytes but also resist interference from the system, aiding in further system differentiation. A new three-dimensional (4,6)-connected Zn(II)-based metal–organic framework with the formula {[Zn 2 (BTDI)(3,5-BBIP)]·2.5H 2 O·2DMF} n ( JXUST-50 ) was solvothermally used with 5,5′-(benzothiadiazole-4,7-diyl)diisophthalic acid (H 4 BTDI), which incorporates benzothiadiazole luminescent groups. JXUST-50 displays a fluorescence “turn-on” effect and a blue-shift behavior toward the H 2 PO 4 – anion in formamide solution, with a limit of detection of 0.50 μM. Remarkably, in a pH-dynamic system regulated by NaOH/HCl, JXUST-50 demonstrates a fluorescence “on–off–on” effect and a blue–red–blue-shift behavior toward the H 2 PO 4 – anion. Furthermore, the fluorescence “turn-on” and blue-shift effect observed between JXUST-50 and H 2 PO 4 – may be attributed to host–guest interaction and an absorbance-caused enhancement mechanism.