Dual-mode sensor based on atomically dispersed CuCu-N2O2 site in a Salen-based covalent-organic framework for electrochemical-colorimetric detection of dopamine and uric acid.

We have developed a novel electrochemical-colorimetric dual-modal sensor based on a metallosalen-based covalent organic framework (Salen-COF) for separate electrochemical quantification of uric acid (UA) and dopamine (DA) and colorimetric screening of their total amount. The Salen-COF was synthesized via a Schiff-base condensation between a bimetallic CuCu-Salen complex and melamine (CuCu-MA-COF), yielding a highly ordered porous architecture featuring atomically dispersed CuCu-N2O2 sites, an extended π-conjugated backbone, and electron-deficient triazine units. This unique combination endows the material with rapid electron transfer kinetics, efficient electrocatalytic capability, and peroxidase (POD)-mimicking enzymatic activity. Leveraging these properties, the resulting electrochemical sensor delivered exceptional performance, giving low limits of detection (LODs) of 0.885 and 1.699 μM within linear ranges from 5 to 50 μM and 80-500 μM for DA, and LODs of 0.991 and 1.637 μM within linear ranges from 5 to 80 μM and 100-500 μM for UA. When simultaneously detecting DA and UA, the electrochemical sensor had the low LODs of 1.375 μM and 1.065 μM within the wide range of 5-500 μM, respectively. Furthermore, the CuCu-MA-COF-based colorimetric sensor showed the low LODs of 10.65 nM and 0.374 μM within the range from 0 to 200 μM for DA and UA, respectively. Critically, this dual-modal sensor demonstrates high selectivity against common interferents, excellent operational stability, outstanding reproducibility, and reliable performance in real-sample analysis, underscoring its strong potential for practical, non-invasive health monitoring in point-of-care settings.