Non-precious cobalt–bismuth binary oxide as a superior catalyst for the highly selective aerobic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid in aqueous solvent

Abstract

Developing highly effective cheap metal oxides is of great value for the 5-hydroxymethylfurfural (HMF) aerobic oxidation to 2,5-furandicarboxylic acid (FDCA) under environmentally friendly conditions. Herein, we synthesized a non-precious cobalt–bismuth binary oxide with rich oxygen vacancies by a facile malic-acid-assisted method and then employed it as a superior catalyst for the HMF aerobic oxidation to FDCA in water. Given the characterization results, the accession of Bi₂O₃ made the (311) facet become the preferential orientation plane for Co₃O₄ in the cobalt–bismuth binary oxide. Then, the oxygen vacancies from Co₃O₄ will be increased due to the greater exposure of Co²⁺ on the dominant exposed (311) facet, which in turn will facilitate the aerobic oxidation of HMF to FDCA. Evaluating the performance of cobalt–bismuth binary oxide in HMF oxidation reactions, an outstandingly high FDCA yield of 98.23% with nearly 100% HMF conversion could be found over CoBi-12 (Co/Bi molar ratio of 12 : 1) under 0.6 MPa O₂ pressure and 110 °C in water for 3 h. The findings of this study can contribute to the development of efficient non-precious metal-based catalysts for the aqueous-phase aerobic oxidation of biomass-derived HMF.