A water-stable Zn(II)-based metal-organic framework as a multifunctional fluorescent sensor for vitamin B₆, Fe³⁺ ion...

A water-stable metal-organic framework Zn-MOF, [Zn₃(tzta)₂(NMP)₂(H₂O)₂]·2H₂O, was successfully synthesized under solvothermal condition using a carboxylate-tetrazolyl ligand H₂tzta (H₂tzta = 2-(2-H-tetrazol-5-yl)-terephthalic acid). Zn-MOF exhibits a three-dimensional (3D) framework structure with rtl rutile topological type. The TGA and PXRD measurements demonstrate the high thermostability and water stability. The solid-state fluorescence emission spectra present that Zn-MOF and H₂tzta exhibit the similar emission peaks. Furthermore, Zn-MOF can be used as a "turn-on" fluorescent sensor to detect vitamin B₆ (VB₆) and cephalexin (CEP) in phosphate buffer solution, and it can also sense Fe³⁺ as a "turn-off" fluorescent sensor in phosphate buffer solution. The limit of detection for VB₆, Fe³⁺ and CEP are 0.080 microM, 0.29 microM and 0.021 microM, respectively. In addition, the fluorescence detection mechanism of Zn-MOF for VB₆, Fe³⁺ and CEP was discussed based on fluorescence resonance energy transfer (FRET), internal filtration effect (IFE) and photon-induced electron transfer (PET). Significantly, a visual film utilizing Zn-MOF@SA was constructed for the detection of VB₆, Fe³⁺ and CEP with high reusability and visuality.