Improved Mechanochemical Fabrication of Copper(II) Oxide Nanoparticles with Low E‑Factor. Efficient Catalytic Activity for Nitroarene Reduction in Aqueous Medium

Copper­(II) oxide nanoparticles (CuONPs) have become an essential material with a wide range of applications in different areas. Although different methodologies are available to fabricate CuONPs, most of them are solvent based, which generate a high amount of waste. Therefore, synthetic methodologies under dry conditions are an interesting alternative for seeking high yields, scale-up, and waste minimization. In this work, we describe an improved and lower environmental impact methodology to synthesize CuONPs through one-step high-energy mechanochemical milling under dry conditions. The methodology proved itself efficient to prepare CuONPs in gram-scale quantities, with 88% yield after 20 min at 1000 rpm and in the absence of additional heat treatment. The CuONPs exhibited a predominantly quasi-spherical morphology and an average size of 7.84 ± 2.08 nm. The nanoparticles showed a surface area of 68 ± 10 m2 g–1 and an energy gap value of 2.28 eV. The catalytic activity of the mechanochemically obtained CuONPs was successfully explored for nitroarene reduction in an aqueous medium. Conversion and selectivity both reached 99% for eight nitroarene examples. The catalyst was reused up to five times in consecutive runs without a significant decrease in the catalytic activity.