Room-temperature preparation of highly efficient NH₂-MIL-101(Fe) catalyst: The important role of -NH₂ in accelerating Fe(III)/Fe(II) cycling

The slow redox rate of Fe(III)/Fe(II) couples is a rate-limiting step for Fenton-like performance of Fe-MOFs. In this study, a series of catalysts (MIL-101) with various p-phthalic acid/2-aminoterephthalic acid (H2BDC/ NH2-H2BDC) molar ratios were prepared using a simple and mild chemical method and applied for catalyzed degradation of bisphenol A (BPA). Interestingly, the -NH2 modified MIL-101(Fe) can adjust Fe-Oxo node by increasing the electron density of Fe(III) in the presence of -NH2 group with high electron density, thus forming Fe(II) in situ in MOFs. Meanwhile, the -NH2 groups used as electron-donors can promote electron transfer, resulting in faster Fe(III)-> Fe(II) half-reaction and active H2O2 to continuously generate center dot OH radical. The BPA degradation and rate constant of Fe-BDC-NH2/H2O2 system are 15.4-fold and 86.8-fold higher than that of FeBDC/H2O2 system, respectively. The density functional theory (DFT) calculations showed that Fe-BDC-NH2 possesses higher Fermi level energy (-4.88 eV) and lower activation energy barriers (0.32 eV) compared with FeBDC. Moreover, Fe-BDC-NH2 showed good reusability and stability. This work offers a highly efficient and stable MOFs-based Fenton-like catalyst to rapidly degrade organic pollutants over a wide pH range for potential applications in wastewater treatment.