Recently, the role of plant-based nanoparticles as sustainable catalysts has emerged as a new eld in material science. As a result of their wide applicability, bio-designed nanocatalysts have dominated the present study. At this juncture, this study gives the rapid and systematic procedure for the formation of an aqueous Elaeocarpus Sylvestris plant leaf extract capped Copper Oxide nanoparticles (ESCuO NPs). A benign method has been established for the fabrication of ESCuO nanoparticles that which serves as an innocuous, renewable, and mild reducing agent. Vivid spectrochemical and optical experimental investigation supported the formation of the ESCuO particles. Based on TEM investigation, the produced ESCuO NPs had spherical shape and an average size of 53 nm. The phytochemicals were used as a reducing agent internally without the use of harmful chemicals or extremely high temperatures. The derived ESCuO NPs have been employed as a powerful catalyst to reduce 4-nitrophenol. Further, rate constants for different doses were calculated. The antioxidant e ciency of synthesised ESCuO NPs was determined. This study illustrates the way for cutting-edge synthesis of CuO NPs with numerous applications.