Rapid oxidation of 4-cholorphenol in the iron-based Metal-Organic frameworks (MOFs)/H2O2 system: The ignored two-steps interfacial single-electron transfer

Fe-based metal-organic frameworks (MOFs) are popular in activating oxidants e.g.H2O2 and persulfate (PS) for degrading recalcitrant organic substances, generally regarded with a simple interfacial efficient iron cycle. This study has revealed that a novel two-steps single-electron transfer mechanism would occur initially to activate the rapid degradation 4-chlorophenol (4-CP) in the MIL-88B(Fe)/H2O2 system (88B/H2O2 system). The degradation of 4-CP was acidic favorable (pH(0) <= 6.0) and could be divided into two reaction stages, i.e., initial lag phase (0-10 min) and following rapid decay phase (10-50 min). In the first stage, H2O2 was slowly activated on the surface of 88B to form superoxide radical (O-2(.-)), which would lead to the accumulation of the key intermediate hydroquinone (HQ) through reducing 4-CP. Afterwards, HQ could reductively dissolve iron ions which would lead to the subsequent efficient homogeneous Fenton reaction for the rapid oxidation of 4-CP by hydroxyl radical (.OH) in the following rapid decay phase. It was interesting to note that specific aromatic compounds, which would form reductive benzenediols intermediates by O-2(.-), could be efficiently degraded in the 88B/H(2)O(2)system. The result of this study is expected to provide a new insight for understanding the catalytic oxidation process based on MOFs, and its application if possible.

Automated summary

This study reveals a mechanism of Fe-based metal-organic frameworks in the rapid degradation of recalcitrant organic substances using oxidants such as H2O2. The process occurs in two stages, activation stage and rapid degradation stage. In the activation stage, H2O2 is slowly activated, forming superoxide radicals. In the rapid degradation stage, the reductive dissolution of iron ions leads to a subsequent Fenton reaction, resulting in the rapid oxidation of organic compounds.