Iron Oxide as a Catalyst for Nitroarene Hydrogenation: Important Role of Oxygen Vacancies

Heterogeneous catalytic hydrogenation of nitroarenes is one of the most important chemical transformations, and exploring earth-abundant catalysts is very attractive for application. Herein, we studied the catalytic activity of several iron oxide catalysts with similar structure and surface area. It is found that gamma-Fe2O3, gamma-Fe2O3, and FeO show obvious but a little limited activity, but the activity of the used catalyst is increased in the second run, especially for gamma-Fe2O3. Characterization shows that Fe2O3 is partly reduced with many oxygen vacancies produced on the surface, which accounts for the high hydrogenation activity. Finally, Fe3O4 exhibits activity significantly higher than Fe2O3 and FeO, and 100% selectivity in the hydrogenation of nitroarenes to anilines. Also, Fe3O4 is easy to separate by a magnetic field and shows excellent recycling stability.