Two Zn-based metal-organic frameworks constructed with the mixed ligands for fluorescence detection of Cu2+ and Co2+

Two zinc-based metal-organic frameworks, namely [Zn(L 1 )(Phen)H 2 O] n ( 1 ) and {[Zn(L 2 )(Phen)]⋅(H 2 O)} n ( 2 ), were successfully constructed by mixed ligands strategy (HL 1 =1,4-benzendicarboxylic acid, Phen=1,10-phenanthroline monohydrate, HL 2 =5-hydroxyisophthalic acid), and characterized by X-ray single crystal diffraction, elemental analysis, powder X-ray diffraction (PXRD), etc. The X-ray single crystal diffraction demonstrate that both 1 and 2 show 1D chain structure. The orbital energies of 1, 2 and ligands have been investigated using the Density Functional Theory (DFT) calculations. The fluorescent sensing experimental revealed that both 1 and 2 exhibited excellent selectivity and sensitivity towards Cu 2+ and Co 2+ ions over other metal ions, and the detection limit (LOD) of Cu 2+ and Co 2+ for 1 were 0.077 μM and 0.15 μM, and the LOD of Cu 2+ and Co 2+ for 2 were 0.81 μM and 0.48 μM, respectively. In addition, the fluorescence quenching mechanism of Cu 2+ and Co 2+ can be attributed to energy competitive absorption. Furthermore, in the real sample detection, the recoveries of Cu 2+ and Co 2+ were 92.6 - 109.1 % and 96.7 - 110.0 %, respectively. This work provided a reliable method for the quantitative detection of Cu 2+ and Co 2+ and was successfully applied in river water with satisfactory recovery and precision.