Herein, the single-atom Ni site heterogeneous catalysts supported by the UiO-66 structure (University of Oslo-66 metal organic framework) were successfully synthesized by a postsynthetic metalation method, where Ni ions are covalently attached to the missing-linker defect sites at zirconium oxide clusters (Zr6O4(OH)4) in as-prepared UiO-66 structure, [Zr6O4(OH)4(BDC)(DMF)10(OH)10] (BDC (benzene-1,4-dicarboxylate), DMF (dimethylformamide)). The structure properties of the catalysts were characterized using powder X-ray diffraction (PXRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), N2 adsorption-desorption isotherms (BET), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and photoluminescence spectroscopy (PL). It was found that single-atom Ni heterogeneous catalysts supported by the UiO-66 structure, UiO-66/Ni1.0 [Zr6O4(OH)4(C8H4O4)(DMF)10(OH)8Ni2(OH)2(Cl)2], showed a sphere-like morphology with a high specific surface area as well as good thermal stability. Specifically, the as-prepared UiO-66/Ni1.0 exhibited the excellent catalytic activity and stability for 4-nitrophenol reduction in terms of low activation energy ( E a = 23.15   kJ   mo l − 1 ), high turnover frequency (76.19 molecules g-1 min-1), and high apparent rate constant ( k app = 0.956 mi n − 1 ). In addition, methylene blue (MB) was also chosen as the organic dye model for catalytic reduction reaction. The k app and TOF for the reduction of MB using UiO-66/Ni1.0 were 0.787 min−1 and 33.89 × 10 20 molecules g−1 min−1, respectively.

In this work, we successfully demonstrated the facile fabrication of highly flexible and floatable Cu2O/rGO on Vietnamese traditional paper (VTP) for the solar-light-driven photocatalytic degradation of the antibiotic ciprofloxacin.

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