Selective detection of Ba²⁺ ions using luminescent probes based on hydrazine-tetra-carboxylate zinc metal-organic...

A zinc-based hydrazine tetracarboxylate coordination material, Zn-MOF-GNU-GGU-9, was synthesized by a solvothermal method and investigated as a luminescent probe for Ba²⁺ detection. FTIR, PXRD, TGA, electron microscopy, EDS/elemental mapping, elemental analysis, and N₂ adsorption/desorption measurements confirmed the formation and predominantly mesoporous material, with a BET surface area of 36.973 m² g^-1. Zn-MOF-GNU-GGU-9 exhibited a preferential fluorescence enhancement response toward Ba²⁺ over the investigated competing species. The developed Zn-MOF-GNU-GGU-9 sensor demonstrated high sensitivity toward Ba²⁺ ions, with a LOD of 2.4 μM and LOQ of 7.28 μM. Time-resolved fluorescence measurements demonstrated pronounced changes in the excited-state decay behavior following Ba²⁺ interaction. DFT calculations revealed a ligand-centered HOMO, a ZnO coordination-region-associated LUMO, and electron-rich oxygen-containing regions as plausible Ba²⁺ interaction sites. The combined experimental and computational results suggest that Ba²⁺ induced modification of the coordination environment, together with possible LMCT-related processes, contributes to the observed fluorescence enhancement. The material showed good resistance to the investigated interferences and afforded Ba²⁺ recoveries of 95.8-98.5% in spiked water samples, demonstrating its potential for Ba²⁺ detection.