Selective hydrogenation of nitroarenes under mild conditions by the optimization of active sites in a well defined Co@NC catalyst

• Published in: Green chemistry : an international journal and green chemistry resource : GC Vol. 22; no. 17; pp. 573 - 5741
• Main Authors: Chen, Shuo, Ling, Li-Li, Jiang, Shun-Feng, Jiang, Hong
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 31.08.2020
• Subjects: active sites; amino compounds; Aromatic compounds; Carbon; Catalysis; Catalysts; catalytic activity; Chemical synthesis; Cobalt; Conversion; coordination polymers; encapsulation; Functional groups; Green chemistry; Hydrazine; Hydrazines; Hydrogenation; Metal-organic frameworks; Nanoparticles; Nitro compounds; nitroaromatic compounds; Optimization; Pyrolysis; Selectivity; Stability; temperature; transmission electron microscopy; X ray photoelectron spectroscopy; X-ray absorption spectroscopy
• ISSN: 1463-9262; 1463-9270; 1463-9270
• DOI: 10.1039/d0gc01835j

The catalytic hydrogenation of aromatic nitro compounds containing multiple functional groups into amino compounds with high conversion rates, selectivity, and stability under mild conditions is a great challenge. Herein, a well defined catalyst (Co@NC) is prepared through the pyrolysis of the Co-centered metal-organic framework (MOF) at the optimized temperature. The as-synthesized catalyst exhibits a high conversion rate and selectivity for the hydrogenation of 12 aromatic nitro compounds with different competing groups into desired amino compounds with hydrazine hydrate under mild conditions (80 °C, 30 min, and 1 atm). The catalyst also shows excellent stability and can be reused over 20 times without considerably losing its activity. It is found that the Co-Nx site is the main active site for catalytic hydrogenation, and the Mott-Schottky effect between the surface Co NPs and N-doped carbon can further promote the hydrogenation reaction. EXAFS, TEM, XPS, and Raman analyses confirm that cobalt nanoparticles (NPs) are properly encapsulated by the N-doped carbon matrix at the optimized temperature, and the Co species maintain a high spin state after the catalysis, which may be responsible for the high performance of Co@NC. This work demonstrates not only a highly efficient catalyst for hydrogenation under mild conditions, but also provides insight into the active sites in Co-based catalysts for hydrogenation. The defined catalyst (Co@NC) is prepared through the pyrolysis of the Co-centered metal-organic framework (MOF), in which Co active species (Co-Nx, surface Co NPs) and particle size play important roles in the catalytic hydrogenation of aromatic nitro compounds.