Two bis-ligand-coordinated Zn(ii)-MOFs for luminescent sensing of ions, antibiotics and pesticides in aqueous solutions.

Two organometallic complexes with two and three-dimensional architectures were constructed by using multiple ligands and Zn(ii) ions: [Zn3(BTC)2(DTP)4(H2O)2]·(H2O)4 (Zn-1) (BTC = benzene-1,3,5-tricarboxylic acid and DTP = 3,5-di(1,2,4-triazol-1-yl)pyridine) and [Zn2(NTD)2(DTP)] (Zn-2) (NTD = 1,4-naphthalenedicarboxylic acid). The as-prepared complexes were characterized by single-crystal X-ray diffraction (SCXRD), elemental analysis, powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and fluorescence analysis. Fluorescence sensing tests revealed that the two complexes are effective, sensitive and selective toward cationic Fe3+ and anionic MnO4 - and Cr2O7 2-. During the antibiotic sensing process, cefixime (CFX) for Zn-1 and nitrofurantoin (NFT) for Zn-2 exhibited the highest quenching efficiencies. For sensing pesticides, the highest quenching efficiencies were exhibited by imidacloprid (IMI) toward Zn-1 and Zn-2. The fluorescence quenching of the complexes that was induced by antibiotics, pesticides and MnO4 - was attributed to both the inner filter effect (IFE) and the fluorescence resonance energy transfer (FRET) effect.