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 Fe-57 Mossbauer spectroscopic characterization. It is proposed that the presence of extra Bronsted 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 Bronsted acid sites) and structural stability (MIL-100(Fe) is stable upon annealing at 280 degrees C despite Fe3+-to-Fe2+ reduction) on the catalytic activity of these two solids, depending on the reaction type.