Accurate regulation of carbon skeletons bonded to Fe-N4 single atom nanozymes for efficient generation of reactive oxygen species

Rational design of single atom nanozymes (SAzymes) could be achieved through the accurate configuration regulation of metal coordination sites, nevertheless, the un-defined carbon environment of traditional SAzymes synthesized by high-temperature pyrolysis makes it difficult to unveil the influence of carbon skeletons with enzyme mimicking activities of SAzymes. Herein, we investigated the relationship between the carbon skeletons and the enzyme mimicking activities through the construction of a series of fully pi-conjugated covalent organic polymer (COP)-based SAzymes with analogous Fe-N4 sites. The experimental results and theoretical calculations demonstrated that carbon skeletons bonded to the Fe-N4 catalytic sites strongly affect the enzyme mimicking activities of COP SAzymes. When the number of benzene rings in carbon skeletons was 1, the COP SAzyme possessed much more remarkable oxidase (OXD) and peroxidase (POD) mimicking activities, and further reducing or increasing the benzene rings would dramatically inhibit the enzyme mimicking activity. Additionally, the fantastic enzyme mimicking activity of COP-1 could be applied to colorimetric detection of biological molecules and degradation of pollutants. These results provide a new perspective for the rational fabrication of SAzymes with high catalytic efficiency.