Luminescent metal-organic frameworks for the detection of nitrobenzene in aqueous media

Abstract

The feasibility of highly water stable Zr-based metal organic frameworks (MOFs: UiO-66-NH2) as a sensing probe material was explored for the detection of the electron deficient nitrobenzene (NB) molecule in an aqueous phase. The probe system was highly sensitive toward the NB molecule within the range of 10-100 ppm with a linear range of 0-30 ppm and a quenching efficiency of around 95% (at 100 ppm). The limit of detection (LOD) of the proposed probe was estimated to be 0.9 ppm. In contrast, this method was not affected sensitively by potential interferences such as other aromatic compounds. For instance, benzene (B), toluene (T), and chlorobenzene (CB) showed reduced quenching efficiencies (<40%). The specificity toward NB molecules for the proposed probe was appreciable in the presence of co-existing components (B, T, and CB). DFT calculations showed that the sensing mechanism was ascribable to electron transfer from the excited missed-linker induced sites of the Zr-OH to the NB molecule. This interaction was confirmed by an FTIR analysis of the UiO-66-NH2-NB material. Therefore, the proposed UiO-66-NH2 probe can be used as a potent sensing material for the NB even at low concentrations in an aqueous medium.