High-Entropy Materials as the Catalysts for Valorization of Biomass and Biomass-Derived Platform Compounds

Relying on the excellent properties of high-entropy materials (HEMs), the high-entropy alloys (HEAs) and high-entropy oxides (HEOs) are considered as the novel heterogeneous catalysts for the valorization of biomass feedstock and biomass-derived platform compounds. HEAs and HEOs are opening up a vast, unknown field of alloy or oxide composition and can realize the catalyst stability with the rocksalt crystal structure by means of configurational entropy. In this paper, the general component and structure of lignocellulosic biomass are concisely introduced. Then, the fundamental character of HEMs including the inherent merit and regulatable property as promising catalytic materials is discussed. Therein, the inherent merits of HEMs are defined as the high entropy effect in thermodynamics, lattice distortion in the structure, sluggish diffusion in dynamics, and the cocktail effect in performance; correspondingly, the regulatable property contains the surface area, the applicability of the element, and the size of nanoparticles. In addition, the valorization of biomass feedstocks including the direct pyrolysis of biomass, the selective transformation of cellulose and hemicelluloses, the utilization of lignin, and the catalytic valorization of furfural (FUR) and 5-hydroxymethylfurfural (5-HMF) as the representative biomass-based platform compounds is discussed, and the obtained valuable reaction products are briefly summarized. Finally, further research orientations for the selective volarization of biomass by the use of HEMs as heterogeneous catalysts is prospected, and the recommendable HEAs and HEOs catalysts including the potential metallic elements are proposed for the biomass pyrolysis, the conversion of (hemi)cellulose, and the transformation of lignin, respectively.