Porphyrin-based covalent organic framework with self-accelerated M-N₄ bimetallic active sites for enhanced electrochemical detection of trace hydrogen peroxide

The ultrasensitive detection of trace hydrogen peroxide (H2O2) has been a fascinating research topic owing to its significant application in environmental monitoring, food safety, and scientific research. In this study, bimetallic porphyrin-based covalent organic framework composites (MWCNTs@Mn/Fe-COF) was prepared by in situ polymerization of Mn porphyrin (MnPor) and Fe porphyrin (FePor) on multi-walled carbon nanotubes (MWCNTs), and a biomimetic enzyme electrochemical sensor was constructed for determination of trace H2O2. The unique topological structure features of COF and the high conductivity of MWCNTs not only ensured highly independent M-N-4 electrochemical active sites, but also guaranteed efficient electron transfer pathways. Especially, the introduction of Mn sites formed a self-accelerated redox cycling between valence states, which significantly improved the electrocatalytic efficiency. Taking advantage of the above advantages, the MWCNTs@Mn/Fe-COF based sensor achieved ultrasensitive detection of H2O2 with a low detection limit of 2 nM. Moreover, the developed sensor has been successfully used to measure trace H2O2 induced by lab-equipped ultrasonic cleaners and in disinfector and apple juice. The constructed sensor in this study has potential application value in the rapid detection of trace H2O2 in real samples, which opened up a new way for the synthesis of bimetallic analog enzymes and the construction of ultra-sensitive electrochemical sensors.