Various morphologies of CuO nanostructures are formed in the presence of organic acids.
Rod-, sphere-, star-, and flower-shaped morphologies of CuO are obtained.
The morphology variations of CuO nanomaterials have been explained.
The catalytic ability of CuO samples toward 4-NP reduction has been compared.
Star-shaped CuO has shown superior catalytic activity toward 4-NP reduction.