MIL-101(FeII3,Mn) with dual-reaction center as Fenton-like catalyst for highly efficient peroxide activation and phenol degradation

Metal organic frameworks are important Fenton-like materials in environment remediation. Nevertheless, the slow Fe(III)/Fe(II) cycling and low H2O2 utilization limit their application. In this study, we develop the ferrous bimetallic MIL-101(FeII3, Mn), which significantly enhanced catalytic performance (5.8 and 31.4-fold higher phenol removal rate and apparent rate constant, respectively) compared with the original MIL-101(Fe). The mechanisms are fully investigated by XPS, EPR and DFT. The Fe2+ substitution affords the mixed-valences of Fe(III)/Fe(II) in the frameworks, which serve as stronger sites for H2O2 activation. Mn in MIL-101(FeII3, Mn) can also function as another reaction center to activate H2O2. Catalysts could coordinate with the π–electrons of pollutants, resulting in the electron transfer from pollutants to MIL-101(FeII3, Mn). Moreover, electrons around Mn atoms tends to transfer to the region of Fe atoms owing to the electronegativity difference, inducing to strengthen the electron-rich Fe micro-region. Therefore, H2O2 was primarily adsorbed onto electron-rich regions where it would be efficiently reduced to •OH, contributing to a higher H2O2 utilization (81.2 %). This study opens new insight into design of Fe-based MOFs as highly efficient Fenton-like catalysts in wastewater treatment.