N-ion doped zinc oxide was synthesized by the mechanochemically induced solvent-deficient method using zinc nitrate hexahydrate and ammonium bicarbonate as the precursors. The synthesis was carried out using different calcination temperatures to investigate the dependence of how calcination temperature affects the crystal structure, bandgap, and photocatalytic activity of the zinc oxide doped with nitrogen. The morphological, structural, and optical properties of ZnO were investigated by thermal analysis (TG/DSC), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), diffuse reflectance spectroscopy (DRS), scanning electronic microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), and N₂ adsorption-desorption (BET). Photocatalytic properties of synthesized materials were determined by methylene blue (MB) degradation in an aqua medium exposed to sunlight. N-ion doped zinc oxide samples calcined at 400, 500, and 600°C are found to be highly efficient photocatalysts, with the MB almost completely degraded after 180 min. Per contra, N-ion doped zinc oxide sample calcined at 300°C is found to be less efficient, most likely caused by different defect chemistry. GRAPHICAL ABSTRACT