Recyclable High-Entropy Oxide Catalysts Unlock Lignocellulose Recalcitrance toward High Yield Xylochemicals

The development of catalysts that are both highly active and structurally stable is critical for addressing the inherent challenges posed by the recalcitrance of lignocellulose, which arises from the complex interconnections and varied chemical properties of lignocellulosic feedstocks. Consequently, there is a pressing need for efficient biorefinery strategies that facilitate the hierarchical separation of these components and their subsequent conversion to valuable chemicals. In this article, we introduce a two-step catalytic process that employs a spinel high-entropy oxide (HEO). This HEO benefits from a "cocktail effect", wherein its high entropy confers numerous intrinsic oxygen vacancies, enhancing its oxygen adsorption and activation capabilities for oxidation catalysis. This approach allows for the efficient refinement of lignocellulose into fine chemicals and exhibits an enhanced performance under mild reaction conditions. The robustness and stability of HEO enable them to sustain a high catalytic activity and effectiveness through multiple catalytic cycles. Finally, we have successfully fractionated lignin into aromatic monomers with a yield of 42 wt % and achieved an impressive total carboxylic acid yield of 150 wt % relative to the original hemicellulose content. Additionally, the cellulose solid fraction, preserved during the HEO treatment, yielded 98.93 wt % glucose when chemically saccharified using a solvent mixture of zinc chloride and formic acid. This strategy represents a significant advance in biomass upgrading, demonstrating markedly higher chemical efficiency in comparison to previously reported methodologies.