Enhanced Oxidation\nof Glucose to Formic Acid under\nMild Conditions Using an Oxygen-Deficient MnO<sub><i>x</i></sub>‑Based Catalyst and a Novel Catalyst Regeneration Strategy

The oxidation of renewable biomass to formic acid using\nmolecular\noxygen over heterogeneous catalysts poses challenges due to harsh\nreaction conditions, limited O<sub>2</sub> activation, and dissolved\ncatalyst recovery issues. In this study, a novel approach utilizing\na vitamin C-assisted and segmented calcination method was introduced\nto synthesize mesoporous MnO<sub><i>x</i></sub> materials\nwith increased oxygen vacancy concentration for the oxidation of biomass-derived\nglucose to formic acid. The catalyst demonstrated a remarkable formic\nacid yield of 69.56% with O<sub>2</sub> as the oxidant under mild\nconditions at 140 °C for 1 h. Furthermore, a simple precipitation\nmethod was developed to recover dissolved MnO<sub><i>x</i></sub> catalysts using MgO to adjust the pH of the solution for catalyst\ncollection. The recovered MnO<sub><i>x</i></sub> with Mg<sup>2+</sup>-intercalated birnessite-like structures could be used again\nwithout any other regeneration treatment. Experimental results indicated\nthat both the initially prepared MnO<sub><i>x</i></sub> and\nthe catalysts obtained through the MgO-assisted precipitation method\nexhibited high concentrations of oxygen vacancies, significantly enhancing\nthe oxidative activity of glucose. This study provides valuable insights\ninto the activation of molecular oxygen at low temperatures for biomass\noxidation and the recovery of heterogeneous catalysts prone to dissolution,\nthereby opening new avenues for sustainable biomass oxidation processes.