Modulating Electronic Structure via Bimetallic D - Band Engineering toward an Ultrasensitive Sensor Platform for Caffeic Acid in Food

To overcome the poor conductivity of pure MOFs and the structural collapse of MOF-derived carbons, this study constructed an electrochemical sensing interface by integrating high-surface-area UiO-66-NH2 with catalytically active bimetallic CoFe alloy-embedded N-doped carbon nanosheets (CoFe@NC). The composite exhibits uniform morphology, clear crystal structure, and a large specific surface area (227.58 m2·g-1), which contribute to enhanced enrichment and detection performance toward CA. This sensor demonstrates a wide linear range (0.001-7 μM) and an ultralow detection limit (0.29 nM), along with excellent anti-interference ability, reproducibility, and stability. By combining density functional theory (DFT) calculations with electrochemical experiments and in-situ Raman characterization, the roles of various components in composite materials during the CA oxidation process, the regulatory mechanism of bimetallic alloys on the electronic structure of the material, the reaction mechanism of CA at the sensing interface, and the synergistic enhancement effect of the bimetallic system were elucidated. When applied to red wine, green tea, blueberries, and apple peel, recoveries of this sensor ranged from 97.2 to 103.8%. The quantitative results were in excellent agreement with those obtained by ultraviolet-visible (UV-vis) spectrophotometry and high performance liquid chromatography (HPLC), confirming the high accuracy and reliability of this sensor. This work not only provides a high-performance sensing platform for trace CA detection in food but also offers a novel strategy for the design and application of electrochemical sensors based on hierarchically structured MOF composites through the deep integration of experimental and theoretical approaches.