Co−Ag−Ce Triple-Phase Interface in Hollow Microreactor with Ag Single-Atom for Directing HMF Oxidation from HMFCA to FDCA

2,5-Furandicarboxylic acid (FDCA) is a biomass-derived precursor obtained from the oxidation of 5-hydroxymethylfurfural (HMF), which can replace terephthalic acid for the preparation of bio-based polymers, and exhibits high structural and thermal stability. To date, HMF-to-FDCA oxidation has suffered from limited mass transfer and poor intrinsic activity, which mesostructural engineering alone cannot fully resolve, particularly regarding atomic utilization and electron transfer. Confining single atoms within MOFs to construct multicomponent catalytic interfaces offers an effective route to atomic dispersion and accelerated electron transfer. Herein, we proposed an in-situ “etching-and-confining” strategy that exploits the redox-ligand-competition synergy of L (+)-Ascorbic acid (VC) to anchor Ag single atoms on hollow, porous CeO₂ that work as “microreactors” for HMF oxidation. Subsequently, two-dimensional Co nanosheets were epitaxially grown on the microreactors outer surface, constructing Co−Ag−Ce ternary catalytic interfaces and rapid “adsorption-diffusion” highways for substrates. Under only 0.5 wt % Ag loading, the catalyst delivers a 90.7% FDCA yield and a TON of 153.4, which is the highest for reported Ag-based catalysts, and retains stable performance for at least ten cycles. The Co−Ag−Ce interface constructed by Ag single atoms that enhances O₂ activation and accelerates charge transfer. Selective poisoning experiments with kinetic analysis uncovers a radical-mediated HMF oxidation mechanism. In addition, it was further utilized for the oxidation of glycerol and benzyl alcohol, achieving a glyceric acid yield of 65.2% and a benzaldehyde yield of 84.6%, demonstrating good applicability and commercial application value.