Heterogeneous Interface Catalysts with Electron Local Exchange toward Highly Selective Oxidation of Biomass Platform Compounds

Catalytic oxidation conversion of biomass-derived compounds to high value-added products has aroused intensive research interest. Herein, we report a Co3O4/Co2MnO4 metal oxide composites catalyst prepared from layered double hydroxides precursors, which is featured with a uniformly interdispersed two-phase heterogeneous interface. This sample exhibits an enhanced catalytic performance for the selective oxidation reaction of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid with a yield of 98%. A combination study including high-resolution transmission electron microscopy (HR-TEM), X-ray absorption fine structure (XAFS), X-ray photoelectron spectroscopy (XPS), and Raman confirms that a strong electron local exchange interaction occurs at the Co3O4/Co2MnO4 heterogeneous interface with electron transfer from Mn in the spinel to Co in the oxide. Both experimental investigations (quasi-in situ XPS, in situ Fourier transform infrared spectroscopy (FTIR), and in situ Raman) and theoretical calculations substantiate that the interfacial metal–oxygen bridge (Co2+–O–Mn4+) serves as an intrinsic active site in determining the reaction pathway: the C═O group in the reactant undergoes activated adsorption at Mn4+, followed by the escape of interfacial lattice oxygen and the oxidation of the aldehyde group to carboxylic acid; subsequently, the O2 molecule undergoes dissociation at the in situ generated oxygen vacancy. This electron local exchange interaction facilitates the mobility of interfacial lattice oxygen, whose universality is demonstrated in catalytic oxidation of other 11 biomass-derived furanoids to the corresponding carboxylic acids.