Preparation, Characterization, and Application of Metal Oxide-Doped Zeolitic Imidazolate Framework

Metal-organic frameworks (MOFs) attract the attention of researchers due to their unique properties, such as high surface area, porosity, and stability. Therefore, in this study, the synthesis of zeolitic imidazole frameworks (ZIF-8), a subclass of MOFs, and copper oxide (Cu₂O) and manganese oxide (MnO₂) containing ZIF-8 was carried out by a mixing method with methanol. The characterization results show that the polyhedral structure of ZIF-8 was prepared with a surface area of 2088 m²/g and a crystallite size of 43.48 nm. Then, each and mixture of two metal oxides were introduced into the ZIF-8 crystal structure. It was found that the surface area and pore volumes of all metal/ZIF-8 samples decreased with metal loading, depending on the type and ratio of metal oxides. The ZIF-8 containing 4.0 wt % Cu₂O and 1.0 wt % MnO₂ had the highest surface area (2084 m²/g), which was closest to that of ZIF-8. The polyhedral structure was maintained by the addition of both metal oxides, and the crystal size of the material decreased with the loading of MnO₂ to the ZIF-8 structure. All of the synthesized samples were analyzed in supercapacitor applications and a relatively higher value of specific capacitance was obtained for Cu-Mn/ZIF-8 due to higher surface area and improved conductivity. In addition to supercapacitor applications, the properties of metal/ZIF-8 are also promising for applications such as catalysts, membranes, and gas storage.