HKUST-1/ZIF-67 Nanocomposites as Heterogeneous Cu–Co-Bimetallic Fenton-like Catalysts for Efficient Removal of Methylene Blue

Fenton-like reactions with Fe-based metal–organic framework (MOF) catalysts have been extensively explored in the field of environmental remediation. However, easy precipitation of Fe2+/Fe3+ and the production of sludge under basic conditions caused catalyst loss and greatly limited their large-scale application in industry. The development of an Fe-free Fenton-like reaction is of extreme importance and remains in its infant stage. Herein, a series of Fe-free dual MOF nanoparticles (HKUST-1/ZIF-67-X) were fabricated by in situ coating of ZIF-67 on HKUST-1 and were systematically analyzed by various characterization techniques, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), and N2 adsorption–desorption isotherms. Subsequently, these materials were applied in catalyzing methylene blue (MB) degradation. The effects of several operation parameters, i.e., pH, H2O2 dosage, catalyst dosage, and reaction temperature, on MB degradation were investigated. It was unveiled that HKUST-1/ZIF-67-7% exhibited an outstanding catalytic activity without the production of any sludge, which could reach as high as 93.29% MB degradation efficiency within 40 min. This was attributed to the unique core–satellite histoarchitecture of HKUST-1/ZIF-67-7% and the synergistic effect between HKUST-1 and ZIF-67. The HKUST-1/ZIF-67-7% composite still achieved up to 80.17% MB degradation efficiency at the fifth catalysis cycle. Importantly, HKUST-1/ZIF-67-7% exhibited significant catalytic efficiency under a wide pH range (4.2–10.1) and top catalytic efficiency at the near neutral pH value. The low cost, environment benignancy, satisfactory degradation efficiency, wide pH application range, and excellent reusability emphasize its great application potential in Fenton-like degradation of pollutants. This contribution could provide a paradigm investigation for designing non-iron-based MOF catalysts to solve the increasingly pressing pollution issues.