Revealing Redox-Driven Multistep Crystallization Mechanism of Cu–Zn Layered Double Salts

Understanding the crystallization mechanism of Zn-based layered hydroxide materials is crucial for the rational design of high-performance catalytic materials. However, elucidating their crystallization kinetics remains challenging owing to dynamic phase and compositional evolution. Here, we provide direct evidence that Cu–Zn layered double salt (LDS) formation proceeds via a redox-driven multistep pathway. Through correlative characterization, we reveal the interplay between metallic precursors and LDS crystallization kinetics, demonstrating that multimetallic interactions critically control LDS structure and morphology. When the reaction starts from metallic Cu with ZnCl2, herbertsmithite (ZnCu3(OH)6Cl2) forms preferentially, whereas starting from metallic Zn with CuCl2 yields a metastable simonkolleite (Zn5(OH)8Cl2·H2O) intermediate and Cu nanocrystals. Subsequently, reoxidized Cu2+ from interfacial Cu nanocrystals intercalates and substitutes for Zn2+ within the simonkolleite framework, inducing Jahn–Teller distortion and driving transformation into Cu–Zn LDS nanocrystals. These nanocrystals grow into hexagonal nanoplates via oriented attachment, followed by their assembly into higher-order flower-like structures. Our results suggest a confinement-enhanced interfacial crystallization model, in which local Zn2+/Cl– enrichment and reduced interfacial tension synergistically promote LDS nucleation and hierarchical growth. These mechanistic insights enable precise control of nonclassical crystallization to tailor the morphology and structure of Zn-based layered materials.