Modulating the Electronic Structure of α-Fe<sub>2</sub>O<sub>3</sub> by Doping Atomically Dispersed Ce for the Transfer Hydrogenation of Nitroaromatics Using Stoichiometric Hydrazine Hydrate
Jinping Zhao, Ganping Wang, Yan Gao, Tongrui Wan, Jiaheng Qin, Xiao Zhang, Fangkun Sun, Jian Fang, Jiantai Ma, Yu Long
Abstract
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.