A flower-like Cu-doped ZIF with intrinsic reference signal for ratiometric electrochemical assay of phenolic compounds

Ratiometric electrochemical probes are vital for reliable sensing but often suffer from complex preparation, reference molecule leakage, and single function. To address these limitations, this study reports a flower-like Cu-doped zeolite imidazolate framework (Zn 0.5 /Cu 0.5 /Co-ZIF) prepared at room temperature via simple stirring. This material acts as both an electrode material and a robust ratiometric probe for detecting catechol (CC) and acetaminophen (AP). Compared with pristine Zn/Co-ZIF, Cu doping confers several advantages: transforming lamellar Zn/Co-ZIF into a flower-like structure for enhanced electron and mass transfer; significantly improving redox current of CC/AP for high sensitivity; and generating a stable Cu-based redox signal as an internal reference, improving accuracy. The sensor achieved wide linear ranges (CC: 0.5–150 μM; AP: 0.2–300 μM) and low detection limits (CC: 0.12 μM; AP: 0.04 μM) for determination of phenol compounds. Compared to single-signal assay, the ratiometric approach showed lower RSDs and superior linear correlations. The sensor also achieved satisfactory simultaneous detection of CC and AP, along with accurate quantification in lake water samples. This work presents a facile strategy for a MOF based reference probe, offering a promising platform for stable and accurate ratiometric electrochemical sensors.