Selective Oxidation of Biomass-Derived Alcohols and Aromatic and Aliphatic Alcohols to Aldehydes with O₂/Air Using a RuO₂‑Supported Mn₃O₄ Catalyst

Selective catalytic oxidation of carbohydrate-derived 5-hydroxymethylfurfural, furfuryl alcohol, and various aromatic and aliphatic compounds to the corresponding aldehyde is a challenging task. The development of a sustainable heterogeneous catalyst is crucial in achieving high selectivity for the desired aldehyde, especially using O₂ or air. In this study, a RuO₂-supported Mn₃O₄ catalyst is reported for the selective oxidation reaction. Treatment of MnO₂ molecular sieves with RuCl₃ in aqueous formaldehyde solution gives a new type of RuO₂-supported Mn₃O₄ catalyst. Detailed catalyst characterization using powder X-ray diffraction, N₂ adsorption, scanning and transmission electron microscopes, diffuse reflectance UV–visible spectrometer, and X-ray photoelectron spectroscopy proves that the RuO₂ species are dispersed on the highly crystalline Mn₃O₄ surface. This catalytic conversion process involves molecular oxygen or air (flow, 10 mL/min) as an oxidant. No external oxidizing reagent, additive, or cocatalyst is required to carry out this transformation. This oxidation protocol affords 2,5-diformylfuran, 2-formylfuran, and other aromatic and aliphatic aldehydes in good to excellent yield (70–99%). Moreover, the catalyst is easily recycled and reused without any loss in the catalytic activity