Nitrogen-Doped Biomass Carbons Meet with Polyoxometalates: Synergistic Catalytic Reductant-Free Aerobic Hydroxylation of Benzene to Phenol

A nitrogen-doped biomass carbon catalyst SFNC(800) was prepared by carbonizing the cheap and readily available soybean flour as the starting material at 800 °C. By combining the SFNC(800) with the Keggin-type V-containing polyoxometalate Ch ₅ PMoV ₂ , a facilely recyclable catalytic system toward liquid-phase reductant-free aerobic oxidation of benzene to phenol was built. The combined catalyst SFNC(800)-Ch ₅ PMoV ₂ exhibited a high activity with 11.2% phenol yield, 14.04 h ^-1 turnover frequency (TOF), and high potential for reusability under the optimized reaction conditions. The present TOF value surpassed almost all the ones of other similar previously reported reductant-free LBTP-O ₂ systems and was even higher than the previous noble metal involved system. On the basis of the characterization results and density functional theory calculations, the structure-activity analysis revealed that the graphitic N-containing moiety in the SFNC(800) is critical to absorb and activate the substrate benzene.