Selective aerobic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid over nanojunctions of cobalt–ceria binary oxide in water

Abstract

Non-precious cobalt–ceria binary oxide was synthesized by a facile citric acid sol–gel method, which can effectively introduce the interfaces into the as-prepared cobalt–ceria binary oxide between CeO₂ and Co₃O₄ and generate nanojunctions. Based on the characterization results, the number of interfaces in the nanojunctions was boosted after introducing CeO₂. These interfaces can alter the surface reactive oxygen species formed and vary the electron transmission process in the cobalt–ceria binary oxide nanojunctions and then tailor the catalytic oxidizability of the cobalt–ceria binary oxide nanojunctions. The electron paramagnetic resonance spectroscopy analysis revealed that ˙O₂⁻ was involved in the aerobic oxidation of 5-hydroxymethylfurfural (HMF) rather than O₂. Given the catalytic performance evaluated on the cobalt–ceria binary oxide nanojunctions, a remarkable 2,5-furandicarboxylic acid (FDCA) selectivity of 90.1% can be obtained over CoCe-15 with almost 100% HMF conversion under molecular oxygen and alkaline conditions. The efficient catalytic performance was dominantly attributed to the interfaces in the cobalt–ceria binary oxide nanojunctions.