Cu-MOF-confined Co nanoparticle nanozymes with synergistic peroxidase-like activity for highly selective colorimetric detection of hydroquinone

Background Hydroquinone (HQ), a widely used industrial chemical, persists in the environment and poses significant health risks, including carcinogenicity, as classified by the WHO. Existing detection methods (e.g., HPLC, GC-MS) rely on sophisticated instruments and complex procedures, limiting their practicality. Colorimetric sensors based on nanozymes offer simplicity and rapidity but often suffer from poor selectivity because of interference from structural isomers (catechol and resorcinol). The development of a high-performance nanozyme with synergistic activity and selective HQ detection remains a critical challenge. Results A bimetallic nanozyme (Cu-MOF@CoNPs) was engineered via a “ship-in-a-bottle” strategy, which successfully confined cobalt nanoparticles (Co NPs) within a porous copper–organic framework (Cu-MOF) scaffold. Characterization (SEM, XRD, FTIR, and XPS) confirmed the successful integration of Co NPs into the Cu-MOF matrix, preserving structural integrity through a pillaring effect while enhancing active site exposure. The composite exhibited superior peroxidase-like activity, with Michaelis constants ( K m ) of 0.39 mM (TMB) and 0.18 mM (H 2 O 2 ), indicating higher substrate affinity than that of natural horseradish peroxidase (HRP). Catalysis was driven by synergistic Cu–Co electron transfer, generating holes (h + ) and superoxide radicals (•O 2 − ). A “signal-off” colorimetric sensor was constructed on the basis of the HQinduced reduction of oxidized TMB (oxTMB), achieving a linear range of 0.2–12 μM, a low detection limit of 65 nM, and high selectivity for HQ over structural isomers (catechol and resorcinol) due to steric confinement and favorable redox kinetics, as verified through expanded interference studies. Practical applicability was validated in tap water, lake water, soil extracts, and cosmetic samples, with recoveries of 94–110% and relative standard deviations <3.5%. Significance The Cu-MOF@CoNPs nanozyme-based sensor provides a cost-effective, portable platform for onsite HQ detection in environmental and consumer safety monitoring. Its high sensitivity, selectivity, and stability highlight the potential of hierarchical MOF-confined bimetallic nanozymes as robust tools for reliable phenolic pollutant analysis.