This research paper demonstrates the synthesis of zero-dimensional (0D) porous cupric oxide (CuO) nanoparticles by two different methods i.e. reflux and precipitation, followed by calcinations at different temperatures starting from 350 to 550 °C with an increment of 100 °C. The synthesized materials when calcined at different temperatures not only retain their structure, but also improve the crystalline nature. The maximum mean pore radius is found to be 4.15 nm for the sample calcined at 550 °C, synthesized by reflux technique, which is confirmed through SANS studies. The Cu (II)-O bond has been recorded in the range of 400 to 600 cm⁻¹ and the peak of Cu-O has been observed at 603 cm⁻¹ which is analyzed through FTIR spectra. The optical band gap of CuO is estimated to be 1.8 eV by diffused reflectance spectroscopic studies which indicate that the synthesized CuO nanoparticles are good photo-catalysts for phenol degradation within the wavelength range of visible-light. However, the polydispersity of the calcined materials gradually decreases with increase in temperature. It has been found from the Hall measurement that the synthesized CuO material is p-type in nature and I–V characteristics are linear in nature. As the Ohmic current mechanism is dominant, therefore the synthesized CuO material is an ideal candidate for sensor applications. The electrical conductivity of the CuO nanoparticles enhances when the measurement has been carried out in presence of phenol. It is seen that 450 °C calcined CuO shows highest degradation efficiency of phenol (98%) and phenol sensing.