Comparison of Porous Iron Trimesates Basolite F300 and MIL-100(Fe) As Heterogeneous Catalysts for Lewis Acid and Oxidation Reactions: Roles of Structural Defects and Stability

Two porous iron trimesates, namely, commercial Basolite F300 (Fe(BTC); BTC = 1,3,5-benzenetricarboxylate) with unknown structure and synthetic MIL-100(Fe) (MIL stands for Material of Institut Lavoisier) of well-defined crystalline structure, have been compared as heterogeneous catalysts for four different reactions. It was found that while for catalytic processes requiring strong Lewis acid sites, Fe(BTC) performs better, MIL-100(Fe) is the preferred catalyst for oxidation reactions. These catalytic results have been rationalized by a combined in situ infrared and 57Fe Mössbauer spectroscopic characterization. It is proposed that the presence of extra Brønsted acid sites on the Fe(BTC) and the easier redox behavior of the MIL-100(Fe) could explain these comparative catalytic performances. The results illustrate the importance of structural defects (presence of weak Brønsted acid sites) and structural stability (MIL-100(Fe) is stable upon annealing at 280 °C despite Fe3+-to-Fe2+ reduction) on the catalytic activity of these two solids, depending on the reaction type.