X-ray diffraction (XRD) patterns for ZIF-8 and ZnO@N-doped C were recorded using Phillips 1700 X'Pert (Cu Kα radiation). The transmission electron microscopy (TEM) and high-resolution TEM (HR-TEM) images for ZnO@N-doped C were obtained using TEM-2100 (JEOL, Japan, operated at accelerating voltage 200 kV). X-ray photoelectron spectroscopy (XPS) was used to investigate the samples' components and monitor the changes in these components. These XPS spectra were collected using a K-alpha instrument (Thermo Fischer, Al Kα radiation), and the peaks were referenced to Zn2p at 1021.7 eV. The UV-Vis absorbance spectra for liquid samples were collected using a Thermo Scientific spectrophotometer (Evolution 300). The UV-Vis diffuse reflectance spectroscopy (DRS) of solid samples were recorded using the Evolution 220 spectrophotometer (Thermo Fisher Scientific, UK). The bandgap energy was calculated according to the equation:-