Metal and metal oxide nanoparticles are gaining traction in inorganic catalysis and photocatalysis, driving the development of eco-friendly methods. This study introduces an eco-friendly and cost-effective approach for synthesizing Al₂O₃ nanoparticles (NPs) using extracts derived from the leaves of Calligonum comosum L. The primary objective of this investigation is to assess the photocatalytic efficacy of the synthesized catalyst in addressing organic pollutants. The Al₂O₃ NPs exhibit a spherical morphology with crystalline arrangements, as evidenced by an average crystallite size of 25.1 nm in the XRD analysis. The band gap energy of the Al₂O₃ NPs is determined to be 2.86 eV. In terms of mechanical properties, the Al₂O₃ NPs show significant potential in enhancing both flexural and compressive properties, thereby making them a viable choice for improving the mechanical performance of composites. Notably, the Young’s modulus of the hybrid composite (comprising plant material and Al₂O₃ NPs) exhibits a remarkable increase of 34.4% in flexion and 78.3% in compression compared to the plant material alone. The catalytic performance of the Al₂O₃ NPs is evaluated using methylene blue (MB) as a cationic dye and Rose Bengal (RB) as an anionic dye. Impressively, the Al₂O₃ NPs demonstrate degradation efficiencies of 98.2% for MB and 90.5% for RB. The degradation processes occur under solar light irradiation, with a contact time of 120 m, a maintained pH of 7, and a temperature of 25 °C. This study found that Al₂O₃ nanoparticles are a promising, cost-effective, and environmentally friendly option for water treatment.