Synergistic depolymerization-oxidation mechanism of Fe3+ catalyzed conversion of cellulose to formic acid

The catalytic oxidation of cellulose to formic acid (FA) using iron-based catalysts represents a promising green technology. However, the role of Fe 3+ is often oversimplified as a mere redox electron-transfer mediator, and the detailed mechanism remains unclear. In this study, a combined experimental and theoretical approach was employed to investigate the dual catalytic mechanism of Fe 3+ in the catalytic oxidation of cellulose. The product yield and structural evolution of solid residues were analyzed under varying reaction times and Fe 3+ concentrations. At the optimal catalyst concentration 0.05 wt%, Fe 3+ not only disrupts cellulose crystallinity by synergistically with H + and suppresses deleterious acid-induced intermediate aggregation, but also governs the selective oxidation of liquid-phase intermediates to FA, achieving a carbon yield of 56.72%. Density functional theory calculations reveal that the identified Fe O complexes significantly reduce the bond-breaking energy of key C C bonds in intermediates, rationalizing the observed synergistic depolymerization-oxidation pathway.