A novel 3D hexagonal honeycomb Zn-MOF for effective detection of Fe3+, CrO42-, and Cr2O72- and selective dye adsorption in aqueous media

Heavy metal ions and organic dye pollutants in water cause serious environmental problems and endanger human health. A 3D honeycomb Zn-MOF, Zn(C22N4O4H12)·16H2O (1), was synthesized by solvothermal reaction with ligand H2L (H2L=2,5-bis-(1H-1,3-benzimidazol-1-yl)-terephthalic acid) as the skeleton and zinc cations as connecting points. The structure of Zn-MOF features one-dimensional channels with a window size of 4.6 Å. The 3D structure is simplified into a (4,4)-binode grid {426282}{4264}. Because of the structural characteristics of Zn-MOF, it exhibits superior luminescent properties and rapid separation of dye molecules of different sizes. The maximum adsorption capacity of Zn-MOF for cationic organic dyes CV, RHB, and JB was as high as 233 mg/g, 218 mg/g, and 168 mg/g, respectively. Luminescent sensing experiments show that Zn-MOF can simultaneously and selectively detect three heavy metal ions Fe3+, CrO42-, and Cr2O72- in aqueous media, and the detection limits are 1.68 μM, 0.15 μM, and 0.46 μM, respectively.