Bio-MIL-100(Fe) Heterostructure Construction and Charge Regulation: Iron Redundancy Breakthrough in a Fenton-like System

Excellent stability and antioxidant properties of MIL-100(Fe) (MF) have made it widely used in water pollution control. However, fully coordinated active sites and slow Fe3+ reduction due to high charge transfer resistance limit the Fenton-like performance of MF. The redox and secondary mineralization capabilities of metal-respiring bacteria (MRB) might be able to optimize and modify MF to address the above bottlenecks. The results demonstrated that MRB (Geobacter) successfully created Fe2+ coordinatively unsaturated sites (CUS) while preserving structural stability and formed a magnetic heterostructure using nonstructurally stable Fe3+. Compared with MF, MIL-100(Fe)-Geobacter (MFG) had 1.6 times iron content and achieved 1.2–4.9 times removal efficiency for different organic pollutants. In addition, MRB secreted extracellular polymeric substances and mediated the formation of Fe3O4 while exhibiting excellent interference resistance and reusability. Density functional theory calculations confirmed that the charge transfer within the heterostructure made the Fe3+ interface electropositive, which overcame the limiting step of the slow Fe3+ reduction rate. Meanwhile, Fe2+ CUS acted to improve the reactivity, which together enhanced the catalytic performance of MFG. This study highlights the potential of MRB as a material modification tool and provides new insights for future biomaterial development and applications in the fields of wastewater treatment.