Fe-porphyrin-based covalent organic framework as a novel peroxidase mimic for a one-pot glucose colorimetric assay

Covalent organic frameworks (COFs) have recently emerged as very fascinating porous polymers due to their attractive design synthesis and various applications. However, the catalytic application of COF materials as enzymatic mimics remains largely unexplored. In this work, the Fe-porphyrin-based covalent organic framework (Fe-COF) has been successfully synthesized through a facile postsynthetic strategy for the first time. In the presence of hydrogen peroxide (H2O2), the Fe-COF can catalyze a chromogenic substrate (3,3',5,5'-tetramethylbenzidine (TMB)) to produce color, and this just goes to show that it has an inner peroxidase-like activity. Moreover, the kinetic studies indicate that the Fe-COF nanomaterial has a higher affinity toward both the substrate H2O2 and TMB than the natural enzyme, horseradish peroxidase (HRP). Under the optimized conditions, the Fe- COF nanomaterial was applied in a colorimetric sensor for the sensitive detection of H2O2. The detection range was from 7 to 500 μM, and the detection limit was 1.1 μM. Furthermore, the combination of the Fe-COF with glucose oxidase (GOx) can be implemented to measure glucose by a one-pot method, and the obtained detection range was from 5 to 350 μM; the detection limit was 1.0 μM. It was proved that the sensor can be successfully used to detect the concentration of glucose in human serum samples. As a peroxidase mimic, the Fe-COF exhibits the advantages of easy preparation, good stability, and ultrahigh catalytic efficiency. We believed that the proposed method in this work would facilitate the applications of COF-based composites as enzymatic mimics in biomedical fields.