Selective detection of Ba2+ ions using luminescent probes based on hydrazine-tetra-carboxylate zinc metal-organic frameworks (Zn-MOF-GNU-GGU-9).

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.