Modulating the Electronic Structure of α-Fe2O3 by Doping Atomically Dispersed Ce for the Transfer Hydrogenation of Nitroaromatics Using Stoichiometric Hydrazine Hydrate

The metal-oxide-catalyzed transfer hydrogenation of nitroarenes to anilines by hydrazine hydrate has been widely reported; however, the risk of explosion resulting from excess hydrazine hydrate and high temperatures and complex preparations of these catalysts immensely hinder their industrial application. Herein, we use a simple co-precipitation method to synthesize atomically dispersed Ce-doped α-Fe 2 O 3 (Ce 0.025 -Fe 2 O 3 -350 °C), which can completely reduce nitroarenes using stoichiometric hydrazine hydrate at room temperature, where the parent α-Fe 2 O 3 is inactive. A thorough characterization indicates that the incorporation of Ce into the crystal lattice of α-Fe 2 O 3 reorganizes the electronic structure of the surrounding Fe, such that the Lewis acidity of Fe 2 O 3 is enhanced, which is the key for the room-temperature decomposition of N 2 H 4 ·H 2 O. The structure is also beneficial for the adsorption of nitroarene, leading to the weakening of the N–O bonds. Mechanistic experiments and DFT calculations demonstrate that the reduction proceeds through Ph-NO 2 → Ph-NHOH → Ph-NH 2 without the widely recognized Ph-NO intermediate. Moreover, Ce 0.025 -Fe 2 O 3 -350 °C exhibits good stability in a continuous-flow reaction.