Fabrication of Cerium‐Doped Manganese Oxide Yolk‐Shell Microspheres for Selective Aerobic Oxidation of 5‐Hydroxymethylfurfural to 2,5‐Diformylfuran

ABSTRACT

Cerium‐doped manganese oxide (CeMnO _x ) yolk‐shell microspheres were synthesized via a microemulsion‐assisted redox precipitation method, and their formation was systematically investigated. The resulting microspheres exhibit diameters of 350–640 nm, with shell thicknesses of 80–170 nm and yolk diameters of 105–230 nm, depending on the Ce/Mn molar ratio. These materials feature homogeneous Ce incorporation within a predominantly γ‐MnO ₂ matrix and a hierarchical porous architecture. Comprehensive characterization reveals that Ce doping not only induces a pronounced morphological transformation but also markedly enhances surface area, porosity, and surface oxygen availability. These improvements are associated with increased structural disorder, weakened metal–oxygen bonding, and the generation of oxygen vacancies. When applied as catalysts for the selective aerobic oxidation of biomass‐derived 5‐hydroxymethylfurfural (HMF) to 2,5‐diformylfuran (DFF), the CeMnO _x materials exhibit strong composition‐dependent activity. An optimal Ce/Mn ratio of 0.08 (Ce _0.08 MnO _x ) affords DFF yields exceeding 85% under mild conditions (120°C, 0.5 MPa O ₂ , 2 h), outperforming other Mn‐based systems on a productivity basis. Mechanistic evidence supports a Mars–van Krevelen pathway in which mobile lattice oxygen drives selective oxidation. These results demonstrate that compositionally and structurally engineered, non‐noble metal oxides can serve as efficient and sustainable catalysts for biomass valorization.