The utilization of low frequency ultrasound (US) offers a straightforward and powerful tool for the production of nanostructured materials, in particular for structurally stable, highly crystalline, and shape-controlled catalytic materials. Herein, we report an unconventional strategy for the synthesis of CuO nanoleaves within 5 min of US irradiation. The as-obtained CuO nanoleaves were found to be selective in the base-free aqueous oxidation of glycerol to dicarboxylic acids (78% yield of tartronic and oxalic acids), in the presence of hydrogen peroxide (H₂O₂) and under mild reaction conditions. Density Functional Theory (DFT) investigations revealed a synergy between the CuO catalyst and H₂O₂ in maintaining the structural integrity of the catalyst during the reaction, creating alternative efficient pathways for the selective formation of dicarboxylic acids. Isotope labeling experiments using H₂ ¹⁸O₂ further confirmed that oxygen from hydrogen peroxide, not from CuO, was preferentially incorporated into the dicarboxylic acid, significantly preserving the monoclinic structure of the CuO catalyst.

In this review paper, we have assembled the main characteristics of partial oxidation reactions (oxidative dehydrogenation and selective oxidation to olefins or oxygenates, as aldehydes and carboxylic acids and nitriles), as well as total oxidation, particularly for depollution, environmental issues and wastewater treatments. Both gas–solid and liquid–solid media have been considered with recent and representative examples within these fields. We have also discussed about their potential and prospective industrial applications. Particular attention has been brought to new raw materials stemming from biomass, as well as to liquid–solid catalysts cases. This review paper also summarizes the progresses made in the use of unconventional activation methods for performing oxidation reactions, highlighting the synergy of these technologies with heterogeneous catalysis. Focus has been centered on both usual catalysts activation methods and less usual ones, such as the use of ultrasounds, microwaves, grinding (mechanochemistry) and photo-activated processes, as well as their combined use.