Cobalt-Ceria Binary Oxide Nanojunctions for Aqueous-Phase Aerobic Oxidation of 5-Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid: The Role of Interfaces

Cobalt-ceria binary oxide nanojunctions were preparedby a sol-gelmethod with various chelating agents. The formed interfaces amongCeO(2) and Co3O4 can promote the generationof nucleophilic O-& BULL;(2) (-) from O-2 and then tune the catalytic oxidizability ofthe as-prepared CoCe nanojunctions. Given the results of HMF oxidations,malic acid as a complexing agent during the preparation process ofthe cobalt-ceria binary oxide nanojunctions can lead to a good catalyticperformance on HMF oxidations to FDCA, and a remarkable FDCA selectivityof 92.3% and almost 100% HMF conversion were obtained at 110 & DEG;Cunder O-2 and alkali conditions. By comparing the catalyticperformance of the nanojunctions and physical mixing of cobalt-ceriabinary oxide on oxidations of HMF, 5-hydroxymethyl-2-furancarboxylicacid (HFCA), and 5-formyl-2-furancarboxylic acid (FFCA), the interfacesintrinsically enhanced the FDCA yield dominantly via boosting theHMF oxidation to HFCA with O-& BULL;(2) (-) during the stepwise oxidation of HMF to FDCA. It can be enlighteningthat the introduction of the active sites for transforming O-2 to O-& BULL;(2) (-) to promotethe transformation of HMF into HFCA is the key to boosting the selectiveaerobic oxidation of HMF to FDCA.