Metal Single-Atom and Nanoparticle Double-Active-Site Relay Catalysts: Design, Preparation, and Application to the Oxidation of 5-Hydroxymethylfurfural

For tandem reactions with several intermediate products, improving the reaction rate of each step is vital for accelerating the entire reaction. However, simultaneously enhancing the conversions of different intermediates using a single-active-site catalyst remains a challenge because the catalyst commonly promotes only one type of reaction. Herein, a Co-based double-active-site relay catalyst (denoted as (Co₁→Co_p)/N-CNTs) is reported. Due to the preferable catalytic activities of Co single atoms (Co₁) and Co nanoparticles (Co_p) for the oxidation of hydroxyls to aldehyde groups and aldehydes to carboxyl groups, respectively, the prepared (Co₁→Co_p)/N-CNTs exhibited good catalytic performance for the aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA). The catalyst achieved 100% HMF conversion efficiency and 96% FDCA yield under a 0.1 MPa O₂ atmosphere at 100 °C for 8 h. The presented strategy offers prospects for the development of highly active catalysts for complex tandem reactions.