Tuning the Chemistry of Fe-Nodes in MIL-100(Fe) through In Situ Generation of High Ratio of Mixed-Valence Sites: The Roles of Site-Specific and Textural Properties in Photo-Fenton Reaction

Several studies were focused on the application of MIL-100(Fe) (Fe3O(OH)(H2O)2(BTC)3, H3BTC is 1,3,5-benzene tricarboxylic acid) in the photo-Fenton reaction, but it still suffers from low efficiency. In this work, MIL-100(Fe) was synthesized at ambient conditions and low pHs using Fe(II) precursors in homogeneous aqueous media to develop a sample with high activity in the photo-Fenton reaction, even better than Fe-porphyrin metal–organic frameworks. The as-synthesized sample is highly crystalline with 30.6% Fe(II)/Fe(III) mixed-valency (equal to 0.92 Fe per node). Since the Fe(II) sites are inserted in the framework during the synthesis process, a lower activation temperature (120 °C) is required to create open metal sites. This strategy can tune the chemistry of Fe-nodes which in turn can significantly improve the photo-Fenton efficiency of the material. Moreover, the mentioned synthesis conditions can optimize the textural properties of the material to increase the diffusion rate of the analytes into the pores and the accessibility of Fe-nodes. Overall, here, it was proved that the chemistry of Fe-nodes of MIL-100(Fe) can be tuned through the in situ generation of high ratio of mixed-valence sites and textural properties to reach high efficiencies in the photo-Fenton reaction.