Non-noble metal catalysts for hydrogenation: A facile method for preparing Co nanoparticles covered with thin layered carbon

• Metallic Co nanoparticles covered by thin carbon layers are prepared.
• Metallic Co is the active phase for hydrogenation reaction.
• The role of carbon layers is to protect Co nanoparticles from overoxidation.
• Surface properties of Co nanoparticles affect the chemoselectivity.

Metallic cobalt nanoparticles with surface CoOx patches covered by thin layered carbon (named Co@C) have been directly synthesized by thermal decomposition of Co-EDTA complex. Raman spectra and HRTEM images suggest that discontinuities can be found in the disordered layered carbon. XPS shows that the CoOx patches in the Co@C nanoparticles can reduced to metallic Co by H2 under reaction conditions (7 bar at 120 °C), and H2–D2 exchange experiments show that the reduced metallic Co nanoparticles covered by carbon layers can dissociate H2. The Co@C nanoparticles show excellent activity and selectivity during chemoselective hydrogenation of nitroarenes for a wide scope of substrates under mild reaction conditions. Based on the results from DRIFTS adsorption experiments, we propose that metallic Co in the Co@C nanoparticles is the active phase. The role of the carbon layers is to protect the Co from overoxidation by air, leading to the chemoselective hydrogenation of nitroarenes.

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