Unraveling in-situ growth mechanism of core-shell β–FeOOH@MnFe–layered double hydroxides composite as efficient peroxymonosulfate activator for multi-pathway contaminant degradation

Engineering core-shell catalysts is an effective strategy to maximize active-sites exposure and enhance interfacial synergy; however, their one-pot formation mechanism and structure-performance relationships remain insufficiently understood. Herein, cauliflower-like β-FeOOH@MnFe-LDHs (FMF) core-shell microstructures were synthesized via a facile hydrothermal route for efficient peroxymonosulfate (PMS) activation and bisphenol A (BPA) degradation. Time-dependent analyses reveal that Fe 3+ initially precipitates as Fe(OH) 3 during urea decomposition, subsequently transforming into β-FeOOH and directing the epitaxial growth of MnFe-LDHs to form a well-defined core-shell architecture. The resulting hierarchical microporous framework offers confined microenvironments that facilitate PMS adsorption and rapid pollutant dissolution, enabling 96% BPA removal and 91% mineralization within 30 min. Electrochemical analyses demonstrate strong electronic coupling between the β-FeOOH core and MnFe-LDHs shell, which accelerates interfacial electron transfer and PMS activation. The FMF10/PMS system generates multiple reactive oxygen species (ROS) including SO 4 ●– , ● OH, O 2 ●– and 1 O 2 through synergistic radical and non-radical pathways. In-situ Raman and post-reaction X-ray photoelectron spectroscopy (XPS) confirm the formation of metastable FMF10-PMS ⁎ complexes via –OH ligand exchange, highlighting the auxiliary role of electron transfer pathway (ETP) in BPA degradation. Owing to its multi-pathway mechanism and self-regenerating bimetallic redox cycle, the FMF10/PMS system exhibits broad-spectrum activity, strong interference resistance, and excellent stability in real water matrices. Three BPA degradation pathways are proposed, and toxicity predictions (ECOSAR and T.E.S.T) indicate a reduced ecological risk of transformation products. This study elucidates the growth mechanism and charge-transfer dynamics of core-shell FMF, offering a scalable strategy for next-generation catalysts in advanced wastewater remediation.