A dinitro-functionalized Zr(IV)-based metal-organic framework as colorimetric and fluorogenic probe for highly selective detection of hydrogen sulphide

The dinitro-functionalized Zr(IV)-based metal-organic framework (MOF) material namely DUT-52-(NO2)2 (1, DUT = Dresden University of Technology) was successfully employed as a fluorescent turn-on probe for the detection of H2S under physiological conditions. 1 was prepared under solvothermal conditions by heating a mixture of ZrCl4, H2NDC-(NO2)2 (H2NDC-(NO2)2 = 4,8-dinitronapthalene-2,6-dicarboxylic acid) ligand and acetic acid with a molar ratio of 1:1:30 in DMF at 130 °C for 24 h. The phase purity of the material was verified by X-ray powder diffraction (XRPD) analyses, infrared spectroscopy and thermogravimetric (TG) analyses. When employed as a fluorescent turn-on probe, the thermally activated 1' exhibited exceptional selectivity and sensitivity for the sensing of H2S under physiological conditions (HEPES buffer, pH = 7.4, temperature = 37 °C). The compound displayed naked-eye colorimetric responses towards H2S under day light as well as under UV radiation with a detection limit of 20 μM, which falls within the range of H2S concentration found in the biological systems. The excellent selectivity of 1' towards H2S is retained even in the presence of other competing biochemical species. In the cellular imaging experiment, J774A.1 loaded with probe 1' showed intense fluorescence in response to H2S. The probe 1' is capable of sensing H2S in blood plasma and in mouse macrophage J774A.1 cells. These features bestow the material with great potentials in the field of H2S detection.