The continual presence of methylene blue (MB) dye in aquatic environments raises considerable health and ecological issues owing to its toxic nature and resistance to biodegradation. In this study, a novel metal oxide hydrogel nanocomposite material, consisting of copper oxide nanoparticle (CuO NPs) doping within acrylic acid graft β-cyclodextrin xanthate-based hydrogel (AGBHs) and referred to as AGBHs@CuO NCs, was synthesized, characterized, and employed for the effective elimination of MB from wastewater. The AGBHs@CuO NCs was produced using a hydrothermal method, resulting in a material that is both highly porous and photoactive. Batch mode experiments were performed to explore the optimization of all the adsorption parameters. The highest removal efficiency of MB by AGBHs@CuO NCs was reached 98.41%. The experimental data were best fitted by the Langmuir isotherm model, indicating monolayer adsorption, with a maximum adsorption capacity of 115.42 mg g⁻1. The relatively high adsorption capacity could be ascribed to the enlarged surface area and porosity, coupled with the complementary interaction between the AGBHs hydrogel matrix and CuO NPs, enhancing the accessibility of active sites and improve dye affinity. The kinetics investigation adhered to a pseudo-second-order model, suggesting a chemisorption mechanism, with rate constant of 4.18 × 10⁻3 g (mg·min)-1. The MB photodegradation was achieved 95.23% within a duration of 50 min, accompanied by a rate constant of 4.39 × 10⁻2 min⁻1. The nanocomposite demonstrated remarkable reusability, preserving adsorption and desorption efficiencies of 87.82% and 85.55%, respectively, after the fourth cycle. In actual wastewater samples, the efficiencies for removal and photocatalytic degradation were 92.64% and 81.47% for the Ami River, while for the Maheshra River, they were 95.22% and 82.86%, respectively. Overall, the AGBHs@CuO NCs shows a potentially high adsorption efficiency and efficient photocatalytic MB degradation, suggesting a robust, durable, and effective adsorbents for the incremental enhancement of adsorptive–photocatalytic removal of MB from water.