Nanoconfined zero-valent iron effectively enhances the catalytic degradation of phenolic pollutants by Fe-Mn bimetallic peroxidase-like compound

Peroxidase mimics can activate H2O2 to degrade organic pollutants in water. A novel bimetallic active center of MOF-based peroxidase-like (POD-like) (Fe@PCN-222(Mn)) was synthesized, with Fe0 uniformly doped within the channels of PCN-222(Mn). This nano-constrained strategy greatly improves the catalytic stability and anti-interference performance of Fe@PCN-222(Mn). Enzymatic reaction kinetics studies showed that Fe0 doping significantly increased the reaction rate. Compared to externally exposed Fe/PCN-222(Mn), pure PCN-222 and PCN-222(Mn), Fe@PCN-222(Mn) exhibited a more stable and efficient performance in the 4-NP-catalyzed degradation process, assisted by both bimetallic synergism and nanoconfinement. Within 60 min, the removal of 4-NP was as high as 100%, while the removal of TOC was 56.74%. The large amount of 1O2 produced in the Fe@PCN-222(Mn)/H2O2 system is the main reason for the rapid degradation of 4-NP. This is because the distance between the pollutant molecules and the ROS is greatly shortened under the nanoconfined conditions, and the electron transfer efficiency between Fe/Mn is also effectively improved. Furthermore, the electronegativity difference between Fe/Mn drives the reaction. This work expands the application of POD-like and offers a new approach to designing and developing Fenton-like catalysts.