Design, Synthesis, and Characterization of TEPE-Zn-MOF as a Turn-On Fluorescent Probe for Pb²⁺ Detection.

The selective detection of Pb²⁺ using fluorescent probes remains formidable. As the most reported sensors suffer from fluorescence quenching and interference from competing metal ions. In order to address this limitation, we synthesized a Zn-based metal–organic framework (TEPE-Zn-MOF) incorporating a π-conjugated tetra(pyridyl)ethene ligand that encourages ligand-centered emission and reachable coordination sites. The resulting framework is structurally robust, crystalline, and thermally stable, which provides an effective platform for fluorescence sensing. TEPE-Zn-MOF reveals strong emission that is largely insensitive to a large range of metal ions. It shows a pronounced turn-on fluorescence enhancement specifically in the presence of Pb²⁺, which is fourfold high in intensity and has a detection limit of 5.1 µM. This selective response is characteristic of chelation-enhanced fluorescence arising from strong Pb²⁺ coordination at pyridyl nitrogen sites, supported by DFT analysis and validated against ICP-MS for real-sample monitoring.