Systematic Determination of Structure‐Activity‐Selectivity Correlations for the Catalytic Oxidation of Glucose to Acetic Acid Depending on the Structure Type of the Used Polyoxometalate Catalyst

The BioValCat (Enhanced Biomass Valorization by Engineering of Polyoxometalate Catalysts) project aims for developing homogeneously catalyzed, selective biomass transformation techniques toward an industrially viable biomass valorization process. The present study sets out the foundations for a scalable, safe, and economic procedure for the oxidation of biomass to valuable products. The extension of the product scope to higher carboxylic acids is of great interest. Herein, we investigate in detail the influence of different polyoxometalate (POM) structure types on the reaction pathways and kinetics for the selective catalytic oxidation of glucose to acetic acid (AA). The results have shown severe structure-selectivity relationships depending on the used POM structure type. Whereas Lindqvist and Anderson-Evans structures promote the [C3 + C3] pathway leading to high AA yields above 20%, Keggin and Wells-Dawson structures are more inclined to follow the [C1 + C5] pathway, resulting mainly in levulinic acid formation. With respect to kinetics, the Anderson-type Na₉TeV₃W₃O₂₄ catalyst showed the highest reaction rate amongst all POMs with 32.62 mmol L^-1 min^-1 _, followed by the Lindqvist-type Na₅V₃W₃O₁₉ with 27.26 mmol L^-1 min^-1, the Keggin-type Na₆PV₃W₉O₄₀ with 21.50 mmol L^-1 min^-1 and the Wells-Dawson-type Na₉P₂V₃W₁₅O₆₂ with a reaction rate of only 14.50 mmol L^-1 min^-1. Overall, the results demonstrate that the reaction pathways and efficiencies in the catalytic oxidation of glucose vary significantly among POMs with different structure types. These findings provide a basis for optimizing the application of POMs in biomass valorization reactions and suggest potential directions for developing more efficient catalysts in the near future.