Synthesis of acidic MIL-125 from plastic waste: Significant contribution of N orbital for efficient photocatalytic degradation of chlorobenzene and toluene

Development of efficient and stable catalyst for the degradation of chlorinated volatile organic compounds (VOCs) is a hot research topic. In this study, we used plastic-based terephthalic acid for the synthesis of MIL-125, which further modified by the -NH2 and -NO2 groups. DFT calculations revealed that the N orbitals had an important contribution in reducing the band gap, leading to easier hydrogen absorption and high electron transfer efficiency. Optical studies, XPS, TRES, NH3-TPD and pyridine IR further demonstrated that the amino modification promoted the visible absorption range and acidity of MIL-125 in comparison to the nitro modification, resulting in efficient catalytic degradation of chlorobenzene and toluene, even in the presence of water. This work provides an economically feasible strategy for modifying metal organic frameworks (MOFs) and suggests the possible VOCs degradation pathways with EPR, in situ FTIR, GC-MS and TG-MS analysis.