Metal-organic framework of Zn(Ⅱ) based on 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine as a highly effective and dual-responsive fluorescent chemosensor target for Fe3+ and Cr2O72− ions in aqueous solutions

The excessive release of chemicals, including Fe3+ and Cr2O72−, may endanger the ecological environment as well as human health. Hence, it is of profound significance to develop effective and accurate sensing and removing strategies. In this work, a series of metal-organic frameworks (MOFs), namely, {[Co(Htpta)(bib)(H2O)]·DMF}n (Ⅰ), {[Ni(Htpta)(bib)(H2O)]·DMA}n (Ⅱ), [Cu(Htpta)(bib)0.5(H2O)]n (Ⅲ), {[Zn4(tpta)2(OH)2(bib)4]·H2O}n (Ⅳ) were synthesized by using 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine (H3tpta), 1,4-bis(1-imidazolium)benzene (bib) and M(CH3COO)2·4H2O (M = Co, Ni, Cu, Zn) under hydrothermal conditions. X-ray single crystal diffraction analyses display that they are assembled into three-dimensional (3D) frameworks via hydrogen bonding interactions and π···π stacking. All MOFs were characterized by infrared spectroscopy, elemental analysis, thermogravimetric analyses (TGA), powder X-ray diffraction (PXRD), X-ray single crystal diffraction and their photoluminescence properties, magnetic and electrochemical properties were also investigated. Among these as-synthesized MOFs, Zn-MOF (Ⅳ) can be regarded as fluorescent sensors with high selectivity and sensitivity to detect Fe3+ and Cr2O72− in aqueous solutions via fluorescence quenching effects and the KSV and limit of detection (LOD) values are comparable to those sensing materials for Fe3+ and Cr2O72– ions. The fluorescence recognition mechanisms were disclosed by PXRD, ICP-AES, ultraviolet-visible absorption (UV–vis) and XPS analyses in detail.