Oxidation Control of 5-Hydroxymethylfurfural to Polymer Building Blocks by Au Clusters and Nanoparticles on Hollow CeO₂ Spheres

Hollow and nanoparticulate Au/CeO2 (Au/HN-CeO2) catalysts were synthesized using hollow microporous organic polymers as templates and applied for the controlled oxidation of biomass-derived 5-hydroxymethylfurfural (HMF) to polymer building blocks, 5-hydroxymethylfuran-2-carboxylic acid (HMFC) and furan-2,5-dicarboxylic acid (FDC). The optimal amounts of Au in Au/HN-CeO2 catalysts resulted in the selective formation of HMFC and FDC with excellent yields of up to 93–96%. The Au-amount-dependent catalytic performance resulted from the cluster and nanoparticle features of Au species in Au/HN-CeO2 catalysts. Au/HN-CeO2 could be recycled in five successive oxidation reactions of HMF to HMFC, maintaining the original catalytic performance.