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

Schematic for the reaction mechanism in MIL-101(Fe II 3 ,Mn)/H 2 O 2 /phenol system. • Novel Fenton-like catalyst MIL-101(Fe II 3 ,Mn) was fabricated. • Fe 2+ substitution constructed the mix-valence of Fe(III)/Fe(II). • Dual-reaction centers was formed via π→cations. • Electronegativity difference enhanced the electron-rich Fe micro-region. • Superior catalytic activity and highly efficient H 2 O 2 activation were achieved. Metal organic frameworks are important Fenton-like materials in environment remediation. Nevertheless, the slow Fe(III)/Fe(II) cycling and low H 2 O 2 utilization limit their application. In this study, we develop the ferrous bimetallic MIL-101(Fe II 3 , 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 Fe 2+ substitution affords the mixed-valences of Fe(III)/Fe(II) in the frameworks, which serve as stronger sites for H 2 O 2 activation. Mn in MIL-101(Fe II 3 , Mn) can also function as another reaction center to activate H 2 O 2 . Catalysts could coordinate with the π–electrons of pollutants, resulting in the electron transfer from pollutants to MIL-101(Fe II 3 , 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, H 2 O 2 was primarily adsorbed onto electron-rich regions where it would be efficiently reduced to •OH, contributing to a higher H 2 O 2 utilization (81.2%). This study opens new insight into design of Fe-based MOFs as highly efficient Fenton-like catalysts in wastewater treatment.