A dinitro-functionalized metal-organic framework featuring visual and fluorogenic sensing of H2S in living cells, human blood plasma and environmental samples.

Abstract

Here, we describe a new dinitro-functionalized Zr(iv) MOF (MOF = metal-organic framework) having a UiO-66 (UiO = University of Oslo) framework topology called UiO-66-(NO2)2 (1). It shows fluorescence turn-on behavior towards H2S in simulated biological medium (HEPES buffer, pH = 7.4). By employing solvothermal conditions, 1 was successfully synthesized by reacting ZrCl4, H2BDC-(NO2)2 [H2BDC-(NO2)2 = 2,5-dinitro-1,4-benzenedicarboxylic acid] ligand and benzoic acid with a molar ratio of 1 : 1 : 10 in DMF (DMF = N,N-dimethylformamide) at 130 °C for 24 h. The material was characterized by infrared spectroscopy, X-ray powder diffraction (XRPD) and thermogravimetric (TG) analyses. The compound not only displays highly sensitive fluorometric sensing of H2S but also exhibits a visually detectable colorimetric change towards H2S in daylight. Moreover, the high selectivity of 1' towards H2S is retained even when several other biologically intrusive species co-exist in the sensing medium. The limit of detection (LOD) of the compound is 14.14 μM which lies in the range of the H2S concentration found in biological systems. Fluorescence microscopy studies on J774A.1 cells revealed the efficacy of the probe for imaging H2S in living cells. Moreover, this material can detect H2S in human blood plasma (HBP) and monitor the sulfide concentration in real water samples. All these features clearly demonstrate that the material has huge potential for highly selective sensing of both extracellular and intracellular H2S.