New Insights into Heavy Metal Sequestration Through Metal‐Phenolic Network‐Confined Nano‐HFO: Overlooking Iron Utilization and Modulating Electron Density

Abstract

Abstract Reducing toxic metal concentrations to trace levels remains a critical challenge in water remediation, largely due to the underutilization of hydrous ferric oxide (HFO), particularly within its inner layers. Herein, we present a novel strategy to enhance HFO utilization by in situ confinement of nano‐HFO within polystyrene beads using a tannic acid‐zirconium (TA‐Zr) metalphenolic network, forming PS‐Fe@TA‐Zr. The TAZr network generates a highly negative microenvironment with tunable electron density at oxygen sites, facilitating Pb(II) enrichment and activating inner‐layer Fe sites. Depth‐profiling reveals a significant increase in the Pb/Fe ratio from 7.6% at the surface to 18.8% at 10 nm depth, highlighting the contribution of previously inaccessible active sites. The TAZr confinement also modulates electron density at Fe and O sites, enabling stronger hybridization with Pb 4f orbitals and enhancing Pb(II)HFO interactions. Compared with PS‐Fe, PS‐Fe@TA‐Zr exhibits over 8‐fold higher selectivity (Kd = 15,278 mL g−1), 5‐fold faster kinetics, and can treat up to 1,680 L kg−1 with effective regeneration across six cycles in actual industrial wastewater. This work provides new insights into metalphenolic network‐assisted design of nanocomposites for highly efficient iron utilization in heavy metal removal.

Keywords

• adsorption
• DFT calculation
• heavy metal
• metal‐phenolic network