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 degrees 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.