Ultrasensitive and Wide‐Range Electrochemical Sensor for Acetaminophen Based on a “Three‐In‐One” Engineered MOF (Fe)@Fe ₃ S ₄ /CNF Platform

ABSTRACT This study presents a novel ternary heterostructured electrochemical sensor (MOF (Fe)@Fe 3 S 4 /CNF) by integrating Fe‐MOFs, Fe 3 S 4 , and carbon nanofibers (CNF) for ultrasensitive acetaminophen (APAP) detection. Fe 3 S 4 was anchored in situ on Fe‐MOFs via ultrasound‐assisted hydrothermal vulcanization, coupled with 3D CNF networks. Characterization (XRD, FT‐IR, SEM, XPS, and BET) confirmed Fe 3 S 4 enhances the MOF electronic configuration via interfacial charge redistribution, while CNF prevents aggregation and boosts conductivity. The optimized sensor shows a wide linear range (0.02–350 μM, R 2 = 0.9993), ultralow LOD (9.583 nM), > 94% interference resistance (UA, DA), and high recovery (97.33%–104.4%). A triaxial synergy mechanism is proposed: (1) MOF mesopores enable size‐selective APAP diffusion, (2) Fe 2+ /Fe 3+ redox pairs drive catalytic activation via Jahn‐Teller effects, and (3) CNF ensures efficient charge transfer. This “pore‐activity‐conductivity” strategy advances MOF‐based sensors through structural precision and interfacial nanoscale engineering for next‐gen electrochemical platforms.