<p>Photocatalysis has emerged as a promising solution to address wastewater-related environmental challenges, such as wastewater treatment. A major challenge in advancing photocatalytic technologies is improving the efficiency, stability, and reusability of photocatalytic materials. This study explores the novel potential of alginate hydrogel as a sustainable and versatile support for two different heterojunction photocatalysts, specifically graphitic carbon nitride (gC₃N₄) combined with CuO (CGCN) and ZnO (ZGCN). The innovation lies in the stabilization of these heterojunction photocatalysts within the alginate hydrogel using sol-gel processing, which not only enhances photocatalytic activity but also provides the photocatalysts with improved moisture retention and reusability. The newly developed ACGCN and AZGCN composites were investigated for the photocatalytic degradation of methylene blue (MB) dye, with a focus on their unique stability and efficiency in extended use. The alginate-based photocatalysts were characterized using instrumental techniques to investigate their physical, chemical, and structural properties. These studies confirmed the successful incorporation of CGCN and ZGCN into the alginate hydrogel, which exhibited characteristic features of photocatalysts. The photocatalytic activity, kinetics, trapping mechanisms, and overall performance of these alginate-based photocatalysts were explored, demonstrating significant potential for sustainable and efficient environmental remediation. The results underscore the novelty of alginate-based photocatalysts with tailored properties for long-term reusability and effective wastewater treatment, setting them apart from traditional photocatalytic systems.</p> Graphical Abstract <p></p>