Stable dye- encapsulated indium- organic framework as dual- emitting sensor for the detection of Hg2+/ Cr2O7 2 and a wide range of nitro- compounds

A water-stable porous anionic metal-organic framework (MOF), [(CH3)(2)NH2][In(TNB)(4/3)]<bold></bold>(2DMF)(3H(2)O) (1, H3TNB = 4,4,4-nitrilotribenzoicacid), was synthesized. Through ion-exchange method, one dual-emitting composite 1DSM was prepared with the encapsulation of cationic dye 4-[p-(dimethylamino)styryl]-1-ethylpyridinium (DSM). 1DSM exhibits sensitive quenching response towards Hg2+ and Cr2O72- ions in aqueous solution. In particular, the detection limit of Hg2+ is as low as 1.75 ppb, which is among the lowest values for MOF-based probes. Moreover, 1DSM shows remarkable sensitivity for nitro-explosives in a wide scope, particularly for phenol hydroxyl-containing nitro-explosives. Furthermore, 1DSM has a broad response to nitroimidazole-based antibiotics at low concentrations. As a result, the incorporation of DSM into MOF could strikingly improve the sensitivity and range of the detection. In addition, the orbital energy theoretical calculation and UV-Vis absorption experiments confirmed that the quenching performances could be mainly attributed to the electron transfer and resonance energy transfer effect between the framework, DSM and the analytes.