Dissolution-Mediated Synthesis of Atomically Thin High-Entropy Hydroxides for Efficient Polyester Glycolysis

Atomically thin high-entropy hydroxides (HEHs) hold great promise for energy and environmental catalysis, yet their controlled synthesis is hindered by two key challenges: (i) thermodynamic incompatibility in multication coprecipitation and (ii) limited thickness control during layered crystallization. Here, this study describes an approach to overcome these obstacles using a dissolution-mediated growth strategy based on the precise regulation of metal cation flux. Our approach leverages the ultrafast NaBH₄-driven coreduction of mixed metal precursors, yielding metastable high-entropy boride (HEB) intermediates. Subsequent atmospheric oxidation gradually destabilizes the HEB lattice, facilitating the diffusion-controlled release of metal cations, which react in situ with hydroxide ions generated by NaBH₄ hydrolysis to form atomically thin HEHs. The high-entropy effect endows the resulting HEHs with a defect-rich atomic architecture, rendering them efficient catalysts for polyester waste recycling. The FeCoNiCuZn-HEH-derived high-entropy metal oxides achieve 100% glycolytic recycling of poly(ethylene terephthalate) (PET), a performance not matched by their low-entropy and medium-entropy counterparts synthesized via the same strategy. The versatile and highly effective synthesis approach presented here not only advances the fabrication of high-entropy materials but also underscores their significant potential for sustainable polymer upcycling.