Visible-light-driven photo-peroxidase catalysis: high-efficiency degradation of indole in water.

The demand for HO restricts the wider application of horseradish peroxidase (HRP) in degradation. In this work, a novel photoenzyme synergistic catalytic system was developed for high-efficiency degrading of indole in water by HRP without extra HO. The HRP was immobilized on CN-ZIF prepared by the combination of g-CN and ZIF-8 to achieve photo-peroxidase catalyst HRP/Zn-CN-ZIF. Under visible light, photogenerated electrons and HO from HRP/Zn-CN-ZIF participated in the biocatalytic cycle of HRP directly. As a result, the indole at 20 mg L in water was degraded completely in 2 h by the HRP/Zn-CN-ZIF photoenzyme synergistic catalytic system without the addition of HO. Furthermore, HRP/Zn-CN-ZIF exhibited superior visible light absorption and charge transfer ability compared to g-CN. The results of the mechanism studies suggest that ·OH would play the most significant role from the HRP/Zn-CN-ZIF in indole degradation. This research provides an efficient approach for the removal of indole from water environments.