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 •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 Fe-BDC/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 Fe-BDC. 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.