Modulating the Electronic Structure of ?-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 alpha-Fe2O3 (Ce0.025- Fe2O3-350 degrees C), which can completely reduce nitroarenes using stoichiometric hydrazine hydrate at room temperature, where the parent alpha-Fe2O3 is inactive. A thorough characterization indicates that the incorporation of Ce into the crystal lattice of alpha-Fe2O3 reorganizes the electronic structure of the surrounding Fe, such that the Lewis acidity of Fe2O3 is enhanced, which is the key for the room-temperature decomposition of N2H4 center dot H2O. 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-NO2-* Ph-NHOH-* Ph-NH2 without the widely recognized Ph-NO intermediate. Moreover, Ce0.025-Fe2O3-350 degrees C exhibits good stability in a continuous-flow reaction.