Additionally, they also found that air could be conveniently used instead of oxygen without affecting the efficiency of the process but required a slightly longer reaction time than O2. They also discovered a commercially available Ru complex with tetrapropylammonium perruthenate (TPAP) that can be used as an effective catalyst for the oxidation of alcohols under the mild reaction conditions with TPAP (5 mol %), CuCl-Phen (5 mol %), 2 equiv. K2CO3, and 1,2-bis(ethoxycarbonyl)hydrazine (DEADH2; 25 mol %) in toluene at 70-80°C with O2. And benzylic, allylic, and secondary alcohols, sulfur heterocycles alcohols, a-ketols benzoin, and primary aliphatic alcohols could undergo smooth oxidation into the corresponding aldehydes and ketones in 56-89% yields. At the same time, a lot of other groups also developed many heterogeneous catalytic oxidation processes since they offer many advantages such as atom utility, better recyclability, a simpler work-up process, lower toxicity, and better selectivity in terms of controllable approaches for reactions compared with the homogeneous ones. Choudary and co-workers developed the heterogenous catalyst Ni-Al hydrotalcite and used it in the direct activation of O2 to selectively oxidize various kinds of allylic and benzylic alcohols, and a-ketols. Corresponding carbonyl compounds were obtained with 31-96% yield with catalyst loading 0.25g/mmol substrate in toluene at 90°C, at atmospheric pressure O2. After 6 th cycle of the catalyst, they could still obtain the oxidized product in 94% yield. Kaneda and co-workers developed the hydroxyapatite-supported palladium nanoclusters and evaluated their application as heterogeneous catalysts in the selective oxidation of alcohols using O2. Using solvent trifluorotoluene at 90-110 °C under an O2 atmosphere for 1-24 hours, the heterogenous Pd-based catalyst PdHAP-0 (Pd 0.2-0.6 mol%) could oxidize a number of aliphatic, aromatic and heterocyclic alcohols having functionalized groups to the corresponding carbonyl compounds in 84-99% yield. Five substrates including primary aliphatic and aromatic alcohols, and secondary aliphatic and aromatic alcohols were successfully oxidized using greener solvent water under 110 °C, 1atm O2, 24 h. Remarkably, the nano clustered Pd 0 species can effectively promote the 250-mmolscale of 1-phenylethanol oxidation with a TON of up to 236 000, and TOF of approximately 9800 h -1 under solvent-free conditions at a little harsh reaction condition of 160 °C, O2, Dean-Stark conditions, 24 h. Other groups also developed heterogenous catalyst oxidation systems using H2O2 as an oxidant instead of O2. Because large-scale aerobic oxidation in the presence of flammable solvents, reagents, and pure O2 at a certain pressure can easily form explosive mixtures, the concentration of oxygen must be strictly limited to prevent combustion or explosive reactions. Varma and co-workers designed a photoactive VO@g-C3N4 catalyst and applied it in the selective oxidation of a variety of alcohols under the photocatalytic reaction conditions (1.5 equiv. H2O2, VO@g-C3N4, CH3CN; 40 W domestic bulb, room temperature). A wide range of primary and secondary alcohols like benzyl alcohol, furfuryl alcohol, aliphatic dihydroxy compounds, and α-hydroxy ketones were converted into the corresponding carbonyl compounds with 85-98% yield. Although H2O2 and pure O2 have been used as greener and more sustainable oxidants in the homogenous and heterogenous catalytic oxidation process, the truly ideal greenest catalytic oxidation reactions, according to the principles of green chemistry, would be used the air directly as an oxidant, since they are more available, cost-effective and no further gas separation or chemical process of oxidants needed. Furthermore, if the selective catalytic oxidation reactions could be carried out in a fully open reaction system under air (as an oxidant), this would be very natural and sustainable, just as plants carry out photosynthesis in a fully developed system in nature. However, to the best of our knowledge, there is no relevant literature report in this regard.