Ligand-regulated growth of various morphologies of copper oxide (CuO) nanostructures has been achieved through an aqueous-based chemical precipitation route where the Cu2+ ions were stabilized through complexation with different organic acids (viz. acetic/citric/tartaric acid). The rod-, spherical-, star-, and flower-shaped morphologies of the CuO nanostructures, obtained in the presence of the different carboxylic acids, have been characterized using XRD, FTIR, HRTEM, DLS, and zeta potential measurements, while their specific surface areas and the associated band gap energies have been compared. The catalytic performance of the different CuO nanostructures has been affirmed by monitoring the reduction of 4-nitrophenol by NaBH4 in real time using UV-visible absorption spectroscopy. The star shaped morphologies of CuO have been found to show maximum catalytic activity toward the reduction of 4-nitrophenol in the presence of NaBH4, which can be correlated to their higher specific surface area and positive surface charge and to the presence of a high indexed facet. (C) 2016 Elsevier Inc. All rights reserved.