A HOF/COF heterojunction-based fluorescence-nanozyme dual-mode sensor for selective detection of tannic acid

This work presents a novel dual-mode sensing platform based on a hydrogen-bonded organic framework/covalent organic framework heterojunction (Namely HOF/COF) for tannic acid (TA) detection. The platform ingeniously integrates the fluorescence recognition capability of HOF with the photoresponsive nanozyme activity of COF. The HOF component introduces abundant hydrogen-bonding sites, enabling specific TA recognition and modulating fluorescence signal through synergistic mechanisms of dynamic quenching, photoinduced electron transfer (PET), and inner-filter effect (IFE). The COF component provides a stable porous framework and exhibits both photoresponsive oxidase-like and peroxidase-like activities, facilitating colorimetric detection. The formation of heterojunction induces significant interfacial synergy, which enhances both detection sensitivity and selectivity. The dual-mode output of fluorescence and colorimetry allows for mutual signal validation, thereby significantly improving the reliability of the assay. The developed sensor demonstrates good performance in the detection of TA in real Rosa roxburghii, teas, and environmental water samples, with good agreement to HPLC method.