(545at) Iron(III)-Based Metal Organic Frameworks As Heterogeneous Fenton-like Catalysts for Organic Pollutants Degradation

Xie Quan

Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Environmental Science and Technology, Dalian University of Technology, Dalian, 116024, China.

Heterogeneous Fenton-like reaction is a promising technology for degrading refractory organic pollutants. Nevertheless, the catalytic performance of heterogeneous catalysts is low and needs to be improved. Iron-based metal organic frameworks have emerged as appealing materials in the field of catalysis because of the high surface area and porous structure, which endow them with sufficiently exposed active sites and favorable mass transfer of reactants. However, their catalytic efficiency for Fenton-like reaction and the relationship between the catalytic efficiency and building units (iron cluster and organic ligands), which is important to clarify the catalytic mechanism, remains unclear. Here, Fe-based MOFs (MIL-88B-Fe, MIL-53-Fe and MIL-101-Fe) with different structures of iron cluster were employed as heterogeneous Fenton-like catalysts. The influence of structures of iron cluster on the catalytic activity was investigated. Furthermore, varying MIL-88B(Fe)-X (X=-NH₂, -CH₃, -H, -Br and -NO₂) with substituent of different electrophilicity on organic ligands were synthesized and the relationship between the catalytic performance and organic ligands was investigated. It was found that MIL-88B-Fe with the highest amount of coordinatively unsaturated irons among three Fe-based MOFs (MIL-88B-Fe, MIL-53-Fe and MIL-101-Fe) presented the best catalytic performance, which was about 1-3 orders of magnitude higher than those for the three conventional catalysts (Fe₂O₃, α-FeOOH and Fe₃O₄). Moreover, the catalytic activity of MIL-88B-Fe could be improved by increasing the electrophilicity of substituent (-NH₂ < -CH₃ < -H < -Br < -NO₂) on organic ligands, which was attributed to the facilitated reduction of Fe(III) to Fe(II) resulted from the reduced electron density of Fe(III) by substituent with high electrophilicity. This work could provide new insights into the rational design and development of highly effective Fenton-like catalysts.