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 Fe 3+ and Cr 2 O 7 2− , 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)(H 2 O)]·DMF} n ( Ⅰ ), {[Ni(Htpta)(bib)(H 2 O)]·DMA} n ( Ⅱ ), [Cu(Htpta)(bib) 0.5 (H 2 O)] n ( Ⅲ ), {[Zn 4 (tpta) 2 (OH) 2 (bib) 4 ]·H 2 O} n ( Ⅳ ) were synthesized by using 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine (H 3 tpta), 1,4-bis(1-imidazolium)benzene (bib) and M(CH 3 COO) 2 · 4H 2 O (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 Fe 3+ and Cr 2 O 7 2− in aqueous solutions via fluorescence quenching effects and the K SV and limit of detection (LOD) values are comparable to those sensing materials for Fe 3+ and Cr 2 O 7 2– ions. The fluorescence recognition mechanisms were disclosed by PXRD, ICP-AES, ultraviolet-visible absorption (UV–vis) and XPS analyses in detail. • Four transition MOFs have been prepared and characterized. • Zn-MOF behaves a dual-responsive fluorescent probe target for Fe 3+ and Cr 2 O 7 2− with high sensitivity, selectivity and anti-interference ability. • The sensing mechanisms of Zn-MOF are discussed in detail.