Construction of an enhanced electrochemical sensor for quercetin in food samples via binary MOF on MOF hybrids.

As the most active antioxidant in the flavonol family, quercetin (QR) exhibits favorable biochemical and pharmacological properties. Therefore, rapid and accurate determination of QR is of great importance. In this study, a π-conjugated molecule, 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) was employed to in-situ grow a conductive metal-organic framework (MOF) on CuCo-zeolitic imidazolate framework (CuCo-ZIF) by a simple one-step solvothermal coating method. This design enhances electron transfer, ultimately yielding a bimetallic MOF-on-MOF hybrid material (CuCo-ZIF@HHTP). The introduction of Cu improves the conductivity of the ZIF framework, while the π-π conjugation characteristic of HHTP further boosts the electrocatalytic performance of CuCo-ZIF. As an electroctalytic eletrode, an electrochemical sensor for sensitive detection of QR was developed, which exhibited excellent linear responses in two concentration ranges (0.25-35 µM and 35-155 µM) with an extremely low limit of detection (LOD) of 7.5 nM (S/N = 3). The sensor also demonstrated high selectivity and reproducibility, with successful application in the quantification of QR in food samples.