<p>A novel hierarchical Fe₃O₄/Fe@C@ZIF-8 composite, which synergistically combined ZIF-8’s superior adsorption capacity with the redox reactivity of the Fe₃O₄/Fe@C core, was synthesized for Cr(VI) synergistic adsorption-reduction. The composite demonstrated remarkable Cr(VI) removal efficiency, achieving 94.27% elimination from aqueous solutions (initial concentration: 30 mg·L⁻¹) under optimized conditions (dosage: 0.6 g·L⁻¹, pH 4.0, 30 ℃). Kinetic and thermodynamic analyses revealed the adsorption process followed pseudo-second-order kinetics and Langmuir isotherm models, indicative of monolayer chemisorption with spontaneous and endothermic characteristics. Mechanistic investigations unveiled a synergistic remediation mechanism: the protonated nitrogen moieties within ZIF-8 enabled electrostatic capture of Cr(VI) oxyanions, which subsequently diffused through ZIF-8’s hierarchical pores to access the Fe₃O₄/Fe@C core; the adsorbed Cr(VI) ions were partially reduced to Cr(III) by Fe⁰, Fe²⁺, and C via intercomponent electron transfer, accompanied by the formation of Fe(III). Consequently, the resulting Cr(III) ions co-precipitated with Fe(III), forming amorphous hydroxide complexes that adhered to the surface of Fe₃O₄/Fe@C@ZIF-8, thereby effectuating the elimination of Cr species from the aqueous environment. Overall, the combination of adsorption, redox transformation, and magnetic separability positioned Fe₃O₄/Fe@C@ZIF-8 as a promising candidate for heavy metal remediation, providing new insights into MOF-based composite design for environmental applications.</p> Graphical Abstract <p></p>