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

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.

Highly efficient and stable hydrodechlorination of chlorophenols in a flow Pd–Ce/SiO2/Ni foam reactor

“…The v/u, v′′/u′′ and v′′′/u′′′ peaks can be attributed to Ce 4+ , while the v 0 /u 0 and v′/u′ peaks are related to Ce 3+ . 54–56 It was found that there are abundant Ce 3+ species existed in the Pd–Ce/SiO 2 /Ni foam reactor, which is well explained by the electron transfer effect between Pd and Ce. The partial reduction of Ce 4+ during the catalyst reduction process may also contribute to the generation of Ce 3+ .…”

Nanoarchitectonics of Non-Noble-Metal-Based Heterogeneous Catalysts for Transfer Hydrogenation Reactions: Detailed Insights on Different Hydrogen Sources

“…The decomposition of N 2 H 4 ·H 2 O results in the formation of N 2 and H 2 and some studies revealed that partial decomposition also occurs to produce NH 3 and N 2 when N 2 H 4 ·H 2 O is used in excess amount. Due to the redox nature of metal species, N 2 H 4 ·H 2 O produces in situ hydrogen protons and metal hydrides, which play a crucial role in transfer hydrogenation reactions. − normalN 2 normalH 4 → normalN 2 + 2H 2 3N 2 normalH 4 → normalN 2 + 4NH 3 …”

Rationally constructing hollow N-doped carbon supported Ru catalysts for enhanced hydrogenation catalysis

“…A heterogeneous catalyst plays an important role in many established and emerging chemical processes, where high performance requires rational design using various synthesized strategies, tuning the geometric structure and microenvironment of active sites, such as coordination status and electronic properties 1–6 Therein, micro- and nanometer-sized materials with hollow interiors as catalysts have attracted particular attention, which demonstrate obvious advantages, such as effectively isolating catalytic species, improving mass transfer, and enhancing the selectivity by controlling pore sizes in the shells. This specific structure can help to achieve excellent performance in chemical synthesis, electrocatalysis, photocatalysis, energy storage and conversion, and other applications.…”