Uncovering the\nLatent Responsiveness of the Water-Stable,\nLuminescent Zn-BDC MOF with Distinct Morphology for Advanced Sensing\nof Nitro Explosives and Ions

Water instability of metal–organic frameworks\n(MOFs) has\nseverely limited their application and practical adaptation. Therefore,\ndeveloping chemically or water-stable metal–organic frameworks\n(MOFs) is a thrust area of research. MOF-5, comprising Zn<sup>2+</sup> and BDC<sup>2–</sup> = 1,4-benzodicarboxylate, reported to\ndate, is a cubic crystal, which degrades within 1 day of water exposure.\nA luminescent, new rod-like Zn-BDC MOF synthesized in water–dimethylformamide\n(DMF) exhibits remarkable stability compared to cubic MOF-5 and other\nMOFs. Its framework remains intact after 6-day water and 3-day acid/basic\nsolution exposures. That is why the distinct rod-like Zn-BDC MOF is\nused further for aqueous analyte sensing to demonstrate its stability\nand optical behavior. Because of instability, most MOF-based luminescent\nsensors in the literature entail nonaqueous medium for sensing. Posing\nexplosive and potential health hazards, nitroaromatic compounds (NACs)\nare detected in liquid, solid, and gas phases via quenching, including\nsome metal ions. Sample characterizations are done by powder X-ray\ndiffraction (PXRD), Fourier transform infrared spectroscopy (FTIR),\nscanning electron microscopy (SEM), UV–vis diffuse reflectance\nspectroscopy (DRS), and photoluminescence (PL). A large Stern–Volmer\nconstant, <i>K</i><sub>sv</sub>, and, in turn, a low limit\nof detection (LOD) for NACs (0.68 μM), Fe<sup>3+</sup> (1.08\nμM), and Cu<sup>2+</sup> (3.08 μM) confirm this distinct\nMOF as a robust and acute sensor in aqueous media. Density functional\ntheory (DFT) is employed on the Zn-BDC MOF to understand stability\nin the presence of different solvents. Mechanistic studies discern\nthat luminescence turn-off arises from competitive absorption and\nelectron transfer processes [resonance energy transfer (RET), photoinduced\nelectron transfer (PET), ground-state electron transfer (GSET), ground-state\ncomplex (GSC), and inner filter effect (IFE)]; for instance, PET and\nRET cause quenching in water. Overall, this study presents a new research\nperspective on improving material stability and accelerating the technological\nadaptation of Zn-BDC MOFs.