Ru Single Atoms for Efficient Chemoselective Hydrogenation of Nitrobenzene to Azoxybenzene

Selectivity control of nitrobenzene hydrogenation remains a great challenge, and it is desirable to develop a green and highly efficient catalytic route toward value-added metastable intermediate products. Herein, we reported that isolated Ru single atoms coordinated with oxygen atoms in CeO2 (Ru-SAs/CeO2) can achieve chemoselective hydrogenation of nitrobenzene to azoxybenzene with a selectivity of 88.2% in a continuous flow reactor using H2 without using any bases or expensive organic reducing agents, while 82.7% aniline selectivity was obtained by Ru nanoparticles. We demonstrated that the unique coordinated structure between Ru single atoms and O atoms preferentially controls the reaction route toward the coupling of nitrosobenzene and phenylhydroxylamine intermediates to form azoxybenzene while greatly suppressing over-hydrogenation. The present work provides an efficient strategy to regulate the reaction pathway of nitrobenzene hydrogenation with a green and industry-friendly process by designing highly dispersed Ru single atoms.