An Ultrastable Luminescent Metal-Organic Framework for Selective Sensing of Nitroaromatic Compounds and Nitroimidazole-Based Drug Molecules

A chemically stable and thermally stable luminescent Cd(II)-based metal organic framework (MOP), [Cd-3(DBPT)(2)(H2O)(4)]center dot 5H(2)O (1), featuring an open Lewis basic triazolyl active site in the host, was successfully assembled by using the multifunctional ligand of 3-(3,5-dicarboxylphenyl)-5-(4-carboxylpheny1)-1-H-1,2,4-triazole (H3DBPT) to bridge hexanuclear {Cd-6} clusters. The host material exhibits ligand-based photoluminescence and solvent-dependent fluorescent intensities, which could selectively, detect nitroaromatic compounds (NACs) of 2,4,6-trinitrophenol (TNP) and 4-nitroaniline (4-NA). The most striking property of 1 is the remarkable sensitivity and selectivity toward TNP and 4-NA even in the presence of other NACs of nitrobenzene (NB), which can be attributed to a photoinduced electron transfer mechanism and resonance energy transfer mechanism. Their photoluminescence quenching could be detected at very low concentrations of 1.14 and 0.70 ppm, respectively, and the maximum quenching efficiencies were found to be 98% and 95%, respectively, at 0.08 mM. Significantly, compound 1 also exhibits excellent sensing performance toward nitroimidazole-based drug molecules of ornidazole (ONZ), metronidazoles (MNZ), dimetridazole (DMZ), and 2-methyl-5-nitroimidazole (2-M-5-MZ), which represents one of the rare MOFs-based fluorescent sensors for simultaneous selective detecting drug molecules and NACs. Their photoluminescence quenching efficiencies increase drastically with the analyte amount even in the low concentration range (<0.15 mM) and reach nearly complete quenching (>95%). The remarkable chemical stability and the unusual sensing performance make this cd-based MOF a promising multiresponsive sensory material for chemical sensing of NACs and nitroimidazole-based drugs.