Fabrication of Aggregation-Resistant SiO ₂ @UiO-66-NH ₂ Electrodes for Sensitive Electrochemical Monitoring of Hydroquinone in Water

Hydroquinone (HQ) is a toxic and persistent phenolic contaminant widely detected in industrial wastewater, posing serious threats to environmental safety and human health. The development of sensitive, selective, and operationally stable sensing platforms for HQ monitoring in aqueous systems, therefore, remains of significant importance. Herein, we report a rationally engineered SiO2@UiO-66-NH2 core−shell nanocomposite as an efficient electrochemical sensing material for HQ detection. In this design, an amino-functionalized UiO-66-NH2 metal−organic framework (MOF) shell is uniformly grown on nonporous silica nanoparticles, effectively suppressing MOF aggregation while retaining high porosity, structural integrity, and chemical functionality. The resulting core−shell architecture integrates the mechanical robustness of the silica core with the porous and functional MOF shell, enabling enhanced electrode dispersion and abundant accessible active sites. When employed as a glassy carbon electrode modifier, the SiO2@UiO-66-NH2 sensor exhibits a wide linear detection range from 5 to 10,000 μM and a low detection limit of ∼0.25 μM. The electrochemical kinetic analyses reveal that HQ oxidation proceeds via a diffusion-controlled, proton-coupled two-electron/two-proton redox process. The superior sensing performance is attributed to efficient analyte preconcentration within the porous MOF shell and selective hydrogen-bonding interactions between HQ molecules and surface-exposed −NH2 groups. The HQ recoveries in the 96−105% range with low RSD (2.29−4.37%) values for real water samples demonstrate this work as an effective core−shell engineering strategy to overcome aggregation, selectivity, and stability limitations of MOF-based electrochemical sensors, highlighting the potential of functional MOF architectures for practical water-quality monitoring applications.