One-Pot Synthesis of Structurally Tunable Ag@Fe3O4 Nanoreactors for Ultra-Efficient and Magnetically Recyclable Reduction of 4-Nitrophenol

The catalytic reduction of toxic 4-Nitrophenol (4-NP) to valuable 4-aminophenol is highly important for environmental remediation. However, developing catalysts with high activity, good recyclability, and facile preparation remains challenging. Herein, Ag@Fe3O4 nanocomposites were controllably synthesized with a facile one-pot polyol method. By varying the Ag:Fe precursor ratio, the structure could be tuned from dense and porous core-shell to Janus architectures. The porous Ag@Fe3O4 nanoreactors (Ag:Fe-0.4) exhibited exceptional catalytic performance, achieving complete 4-NP reduction within 75 s, with an apparent rate constant (k) of 6.29 × 10−2 s−1, a normalized rate constant (kn) of 3742 s−1 mmol−1, and a TOF value of 1042 h−1. XPS results verified that the excellent activity originated from the porous structure and interfacial charge transfer from Ag to Fe3O4. The catalysts showed super-paramagnetism and could be reused for at least eight cycles with >95% conversion retained. It also displayed high efficiency in reducing diverse nitroaromatics and in natural water. This work highlights the significance of structural and electronic modulation, providing a scalable strategy for magnetically recyclable catalysts toward environmental remediation and heterogeneous catalysis.