Structural and catalytic investigation of mesoporous iron phosphate

The local structure of ordered mesoporous iron phosphate, prepared through coassembly of inorganic species and sodium dodecyl sulfate template under the assistance of HF, has been investigated with several physicochemical methods, including small-angle XRD, TG-DSC, and combined spectroscopic characterization of FT-IR, Far-IR, Raman, UV-vis, and XPS. The redox property has also been measured by using the H₂-TPR method. The results of TEM and nitrogen sorption show the mesoporous iron phosphate possesses a well-established mesostructure, narrow pore size distribution, and large surface area (423 m ²/g). The results of the spectroscopic characterization reveal that the mesoporous iron phosphate has specific iron-oxygen and phosphorus-oxygen local environment, differing from those in its crystalline counterpart. Compared with a crystalline sample, the iron-oxygen polyhedrons in the mesoporous sample shows a characteristic of distorted configuration, while the phosphate roots have a shorter P-O bond. Fluorine species are detected by XPS measurement. These factors cause the reduction by hydrogen of the mesoporous iron phosphate to be difficult. The hydroxylation reaction of phenol in glacial acetic acid by hydrogen peroxide has been used as a probe reaction to test the catalytic property of the mesoporous iron phosphate. Better catalytic performance and unique distribution of products has been observed on the mesoporous sample, compared to the crystalline ion phosphate. Finally, a model about the surface structure and reaction network of the hydroxylation of phenol on iron phosphate is proposed.