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 γ-Fe 2 O 3, α-Fe 2 O 3, and FeO show obvious but a little limited activity, but the activity of the used catalyst is increased in the second run, especially for γ-Fe 2 O 3 . Characterization shows that Fe 2 O 3 is partly reduced with many oxygen vacancies produced on the surface, which accounts for the high hydrogenation activity. Finally, Fe 3 O 4 exhibits activity significantly higher than Fe 2 O 3 and FeO, and 100% selectivity in the hydrogenation of nitroarenes to anilines. Also, Fe 3 O 4 is easy to separate by a magnetic field and shows excellent recycling stability.