Unravelling the impact of lower vacuum activation temperature on Fe2+/Fe3+ mixed-valence unsaturated iron centres in MIL-101(Fe) and its impact on Fenton degradation of acetaminophen

The impact of varying activation temperatures under vacuum on the Metal-Organic Framework (MOF), MIL-101(Fe), and its consequential effects on H₂O₂ activation and Fenton degradation of one of the contaminants of emerging concerns, acetaminophen (ACT) is investigated in this work. MIL-101(Fe) underwent vacuum activation at temperatures ranging from 60 ℃ to 150 ℃, and an in-depth analysis of the resulting samples' physical and chemical properties were conducted. XRD, FTIR and microscopic studies revealed that the structure and crystallinity of the samples were preserved irrespective of the activation temperature. MIL-101(Fe) activated at 120 ℃ (MIL-101–120) demonstrated the highest degradation kinetics when examined for Fenton degradation of ACT. XPS analysis revealed that MIL-101–120 exhibited the highest Fe²⁺: Fe³⁺ ratio and a complete degradation of ACT was attained within 60 minutes of the reaction. This indicated a direct correlation between increased Fe²⁺ content and the rate of Fenton degradation. A possible catalytic mechanism for the ACT degradation by MIL-101(Fe) was further proposed, indicating the influence of different active sites and radicals in the reaction. Overall, the study provides insight into the significance of optimizing various activation conditions to improve the catalytic efficiency of MIL-101(Fe).