Metal organic frameworks based on mixed ligands: Syntheses, structures and selective detection of nitro explosive TNP, metal ions Fe3+ Cu2+ and CrO42-

Three new MOFs [Cd(2,5-bipi)(5-hip)]n (1), [Mn(2,5-bipi)(1,3-bdc)]n (2), and [Co(2,5-bipi)(1,3-bdc)(DMF)]n (3) (2,5-bipi = 2,5-bis(1-imidazoly)pyridine, 5-H2hip = 5-hydroxyisophthalic acid, 1,3-H2bdc = isophthalic acid) have been successfully synthesized under solvothermal conditions. They were characterized by elemental analysis, FT-IR spectra, X-ray single-crystal diffraction, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA). The results suggest that the linkage of different ligands with metal ions affords a 4-connected layer. And these 2D networks are extended to the final 3D supramolecular architectures by CH∙∙∙π stacking interactions. Fluorescence sensing measurements showed that MOF 1 can detect TNP, Fe3+, Cu2+ and CrO42− ions with high selectivity and sensitivity. In addition, their possible quenching mechanisms were studied in detail.