Biomass-based N doped carbon as metal-free catalyst for selective oxidation of d-xylose into d-xylonic acid

Rational design and facile preparation of low-cost and efficient catalysts for the selective converting of biomass-derived monosaccharides into high value-added chemicals is highly demanded, yet challenging. Herein, we first demonstrate a N doped defect-rich carbon (NC-800-5) as metal-free catalyst for the selective oxidation of d-xylose into d-xylonic acid in alkaline aqueous solution at 100 °C for 30 min, with 57.4% yield. The doped graphitic N is found to be the active site and hydroxyl ion participating in the oxidation of d-xylose. Hydroxyl ion and d-xylose first adsorb on NC-800-5 surface, and the aldehyde group of d-xylose is catalyzed to form germinal diols ion. Then, C–H bond break to yield carboxylic group. Furthermore, NC-800-5 catalyst shows high stability in recycled test.