We demonstrate a simple template-free green method to prepare copper oxide (CuO) nanoporous material using copper acetate as a single precursor withPiper nigrum(Indian black pepper) dried fruit extract as a reducing medium under microwave irradiation. The surface properties and morphology of the obtained CuO material were assessed using powder X-ray diffractometer, X-ray photoelectron spectrometer, field-emission scanning electron microscope with elemental mapping analysis, focused ion beam high-resolution transmission electron microscope, and N(2)adsorption-isotherm techniques. The characterization results reveal that the prepared CuO is a single monoclinic crystalline phase, and nanoporous in morphology with a specific surface area of 81.23 m(2)g(-1)and containing pore sizes between 3-8 nm. Nanoporous CuO showed excellent electrochemical energy storage performance with the specific capacitance of 238 Fg(-1)at 5 mVs(-1)when compared with commercially available CuO (75 Fg(-1)). Also, nanoporous CuO showed efficient desalting performance in the capacitive deionization system. This eco-friendly synthesis derived nanoporous CuO can be applied as high-performance supercapacitor material for high-energy storage devices and desalination processes.