Zinc(ii)-organic framework as a multi-responsive photoluminescence sensor for efficient and recyclable detection of pesticide 2,6-dichloro-4-nitroaniline, Fe(III) and Cr(VI)

A 2D zinc(ii) metal-organic framework (Zn-MOF-1) formulated as [Zn-2(L)(2)(TPA)]2H(2)O, (L = 4-(tetrazol-5-yl)phenyl-4,2:6,4-terpyridine, TPA = terephthalic acid) was successfully obtained under solvothermal conditions. Zn-MOF-1 shows a new 2D double-layered honeycomb structure containing Zn2+ ions, ligand L and TPA, with uncoordinated nitrogen atoms (from pyridine rings and tetrazol rings) of L and uncoordinated carboxylate oxygen atoms of TPA, which easily form hydrogen bonds with analytes. Fluorescence analysis reveals that Zn-MOF-1 generates strong blue luminescence, which can be assigned to ligand-centered emission. More importantly, it is the first reported recyclable multi-responsive Zn-MOF fluorescence sensor for pesticide 2,6-dichloro-4-nitroaniline, Fe(iii) and Cr(vi) (CrO42-/Cr2O72- ions) detection with high sensitivity, selectivity and low detection limit in methanol or water via fluorescence quenching. Furthermore, selective sensing by Zn-MOF-1 of 2,6-dichloro-4-nitroaniline, Fe3+ ions, and CrO42- or Cr2O72- ions can mainly be attributed to the absorption by the analytes of the excitation and/or emission light of Zn-MOF-1 and the electronic interactions between Zn-MOF-1 and the analytes.