Single-Atom Ni Heterogeneous Catalysts Supported UiO-66 Structure: Synthesis and Catalytic Activities

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), N-2 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)(8)Ni-2(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 (Ea=23.15 kJ mol-1), high turnover frequency (76.19 molecules g(-1) min(-1)), and high apparent rate constant (kapp=0.956min-1). In addition, methylene blue (MB) was also chosen as the organic dye model for catalytic reduction reaction. The kapp and TOF for the reduction of MB using UiO-66/Ni1.0 were 0.787 min(-1) and 33.89x10(20) molecules g(-1) min(-1), respectively.

Automated summary

In this study, single-atom Ni site heterogeneous catalysts supported by the UiO-66 structure were successfully synthesized and characterized, showing excellent catalytic activity and stability in the reduction of 4-nitrophenol and methylene blue. The catalyst exhibited low activation energy, high turnover frequency, and high apparent rate constant for 4-nitrophenol reduction, while achieving a high rate constant and turnover frequency for methylene blue reduction.