A Stable Zn ^II Metal–Organic Framework with a Benzothiadiazole Carboxylate Ligand as Fluorescent Sensor for Zr ^{4 <b>+</b>} , H ₂ PO ₄ ^– , and VB1 in Living Cells

A new N/O polydentate ligand with benzothiadiazole units (4-(7-(1<i>H</i>-pyrazol-4-yl)benzo[<i>c</i>][1,2,5]thiadiazol-4-yl)benzoic acid, H₂PZBTB) has been used to synthesize a stable zinc(II) metal-organic framework (MOF) under solvothermal conditions with the formula {[Zn₂(PZBTB)₂(H₂O)₂]·0.5DMF}_<i>n</i> (<b>JXUST-60</b>, where <b>JXUST</b> denotes Jiangxi University of Science and Technology; DMF = dimethylformamide). <b>JXUST-60</b> possesses a two-dimensional (2D) planar architecture, while interlayer interactions via π-π stacking result in the formation of a three-dimensional (3D) packing structure. <b>JXUST-60</b> maintains structural integrity after being immersed in water and aqueous solutions with pH = 3-13 for 24 h. Fluorescence sensing experiments demonstrate that <b>JXUST-60</b> can function as a turn-on MOF sensor for Zr⁴⁺, dihydrogen phosphate (H₂PO₄^-), and vitamin B1 (VB1) through naked-eye recognition, with low detection limits of 0.06, 0.13, and 0.09 μM, respectively. It is worth noting that <b>JXUST-60</b> is a rare sensor that recognizes VB1 through the turn-on effect and is the only Zn^II MOF fluorescence sensor capable of recognizing Zr⁴⁺ to date. In addition, the cyclic test demonstrates that <b>JXUST-60</b> is a reusable sensor material. More importantly, <b>JXUST-60</b> has good biocompatibility and low cytotoxicity to sense VB1 in living cells.