Co single atoms/nanoparticles over carbon nanotubes for synergistic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid

The preparation of high-value 2,5-furandicarboxylic acid (FDCA) from biomass-based platform compound 5-hydroxymethylfurfural (HMF) is an important synthetic reaction, as the resulting FDCA holds promise to replace terephthalic acid to produce environmentally friendly polyester materials. However, due to the complex tandem nature of the oxidation of HMF to FDCA, which involves several stable intermediates, efficient conversion of HMF and achieving a high FDCA yield remain challenging. Herein, a catalyst of Co SAs/NPs@N-CNTs comprising Co single atoms (Co SAs) alongside Co nanoparticles (Co NPs) supported on carbon nanotubes (CNTs) was synthesized. Co SAs/NPs@N-CNTs exhibited outstanding catalytic activity for the selective oxidation of HMF to FDCA, achieving 100% HMF conversion and 94.2% FDCA yield. This remarkable performance was attributed to the synergistic effect between Co SAs and Co NPs. Poisoning and acid treatment experiments indicated that Co SAs served as the active sites, while Co NPs did not directly act as active sites. Instead, Co NPs merely assisted the Co SAs on the sidelines, facilitating the efficient conversion of HMF into various intermediates and promoting the further conversion of these intermediates into FDCA, thereby achieving high FDCA productivity. This strategy offers new insights for designing efficient catalysts for complex tandem reactions.