P,N co-doped biomass carbon as a remarkable metal-free catalyst for solvent-free oxidation of benzyl alcohol with ambient air: The key promoting role of N co-doping

Benzaldehyde is an important chemical intermediate, and its production via the oxidation of benzyl alcohol with O-2 is highly pursued as an alternative for the existing industrial process to meet the demand of green chemistry. Most of the reported catalytic systems are dependent on the noble/toxic metal catalysts. Herein, a biomass carbon catalyst doped with P and N heteroatoms is prepared by calcinating the phosphoric acid-treated N-containing biomass of soybean flour in N-2. In the absence of solvent or additive, the obtained P,N co-doped carbon catalyst exhibits a remarkable catalytic activity for oxidation of benzyl alcohol to benzaldehyde with air (99.4% yield, TOF = 62.1 x 10(-4) mol BAD/(g catalyst x h reaction time)). The present turnover frequency surpasses all the previously reported ones of similar metal-free carbon catalysts for this reaction. The N co-doping facilitates the P doping into the carbon matrix, favors the formation the catalytic active species and has a remarkable electronic effect on them, which are identified via experiments and DFT calculations.

Automated summary

A biomass carbon catalyst doped with P and N heteroatoms demonstrates high catalytic activity for the oxidation of benzyl alcohol to benzaldehyde in the absence of solvent or additive, surpassing all previously reported metal-free carbon catalysts for this reaction in terms of turnover frequency.