Biosynthesis of C-dots using black mulberry fruit as a precursor for C-dot synthesis is a novel approach. We successfully synthesized C-dots from the fruit extract by employing a hydrothermal autoclave. This green synthesis method offers a sustainable and environmentally friendly route for C-dot production. Our results demonstrate the efficient degradation of pollutants under visible light irradiation, indicating the strong photocatalytic activity of the C-dots. This finding has implications for environmental remediation and the elimination of harmful substances, showcasing the potential practical applications of C-dots in addressing water contamination issues. We made an effort to identify the optimum doping concentration of C-dots and found that 0.2 mol% was the sweet spot. At this concentration, the photodegradation of pollutants reached an impressive 95.8%. The enhanced photocatalytic activity can be attributed to increased electron trapping due to more surface sites and different absorption wavelengths. This work contributes to the synthesis of carbon dots using black mulberry fruits as a sustainable precursor, as well as the comprehensive analysis of their optical and photocatalytic properties.