Highly Efficient Catalytic Oxidation of Inert C(sp³)–H Bonds by the Synergistic Effect of Copper Nanoparticles/N‐Doped Graphene

Abstract

The applicability of Cu is still limited in the heterogeneous catalytic oxidation of C(sp3)–H bonds. This problem was resolved by exploiting the synergistic effect existing between Cu nanoparticles (Cu NPs) and N‐doped graphene. We demonstrate a highly efficient, green protocol for the catalytic oxidation of inert C(sp3)–H bonds with only oxygen as the oxidant catalyzed by Cu NPs/N‐doped graphene (Cu‐N‐rGO). The new composite materials were obtained through a very simple one‐pot solvothermal process. Remarkably, newly prepared Cu‐N‐rGO showed 34.5 % conversion and 89.2 % selectivity for the catalytic oxidation of cyclohexane to KA oil [mixture of cyclohexanone (K) and cyclohexanol (A)] in a single cycle and thus exhibited significantly higher efficiency than the N‐free Cu catalysts. Cu‐N‐rGO has good stability because the doped nitrogen atoms allow strong interactions between the Cu species and graphene, so that the conversion and selectivity can be maintained over five runs. The delicate relationship between the Cu NPs and nitrogen was investigated by accurate control of the ratio of nitrogen and Cu in doped graphene. A hypothesized free‐radical chain mechanism and a peroxidative oxidation process were proven and explained, and the synergistic effect of the Cu NPs and N‐doped graphene in facilitating the oxidation process was also elucidated.

Nitrogen-doped graphene loaded non-noble Co catalysts for liquid-phase cyclohexane oxidation with molecular oxygen

“…However, active metal nanoparticles tend to aggregate due to the low binding energy of metal nanoparticles (NPs) anchored on the original graphene surface [25]. Hence, researchers developed various strategies to stabilize metal NPs on graphene, and substitutional doping the graphene matrix with heteroatoms (mainly nitrogen and boron) represents a convenient route [26]. The aggregation of metal NPs is greatly restricted because of the enhanced metal-support interaction by the strong bonding between N doping sites and metal NPs [27][28][29].…”

Bimetallic oxide nanoparticles confined in ZIF‐67‐derived carbon for highly selective oxidation of saturated C–H bond in alkyl arenes

“…The nitrogen dopant activated the electronic effect of Pd NPs and further enhanced the adsorption and activation of the substrates. Sun et al [ 16 ] deposited Cu NPs on the N‐doped graphene and used in inert C–H bonds selective oxidation. The enrichment of electron density in the carbon matrix by the N atoms promoted the charge transfer between metal and graphene, which greatly increased the conversion of substrates.…”

Clean Oxidation of (Hetero)benzylic Csp3–H Bonds with Molecular Oxygen

“…Compared to conventional inorganic or organic oxidants, molecular oxygen is a perfect oxidant because of its environmental benignancy, low cost, and natural abundance. − Over the past decades, significant achievements have been obtained in the oxidation of alkyl aromatics with dioxygen catalyzed by transition metal–ligand complex, uncommercialized metal-supported catalyst, or activated carbon catalyst (Scheme b). − Nevertheless, those protocols suffer from limitations of requirement of catalyst, tedious procedures, and meagre substrate generality, and few methods are available for the direct oxidation of heterobenzylic C sp3 –H bonds to construct heteroaryl ketones and dioxygenation products. Due to the low threshold of transition-metal residual tolerance for pharmaceuticals, it is highly desirable to synthesize them under transition-metal-free conditions.…”