Designing efficient 2D-bismuth oxychloride (BiOCl)/2D-g-C₃N₄ heterojunction photocatalysts by the microwave-assisted method was studied in this work using different amounts of BiOCl plates coupled with g-C₃N₄ nanosheets. The effects of coupling the 2D structure of g-C₃N₄ with the 2D structure of BiOCl were systematically examined by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy, X-ray diffraction, photoluminescence (PL), lifetime decay measurement, surface charges of the samples at various pH conditions, and UV–vis diffuse reflectance spectroscopy (UV–vis DRS). The prepared photocatalysts were used for the degradation of amine-based pharmaceuticals, and nizatidine was used as a model pollutant to evaluate the photocatalytic activity. The UV–vis DRS and other optical properties indicated the major effect of coupling of BiOCl with g-C₃N₄ into a 2D/2D structure. The results showed a narrowing in the band gap energy of the composite form, whereas the PL and lifetime analysis showed greater inhibition of the electron–hole recombination process and slightly longer charge carrier lifetime. Accordingly, the BiOCl/g-C₃N₄ composite samples exhibited an enhancement in the photocatalytic performance, specifically for the 10% BiOCl/g-C₃N₄ sample. Moreover, the zeta potential of this sample at different pH values was evaluated to determine the isoelectric point of the synthesized composite material. Consequently, the pH was adjusted to match the isoelectric point of the complex materials, which further enhanced the activity. Further degradation of pharmaceuticals was studied under solar light irradiation, and 96% degradation was achieved within 30 min.