Nitrogen and oxygen-doped metal-free carbon catalysts for chemoselective transfer hydrogenation of nitrobenzene, styrene, and 3-nitrostyrene with hydrazine

• Doping of nitrogen and oxygen is effective for the preparation of carbon catalysts.
• The carbon catalysts prepared are active for transfer hydrogenation with hydrazine.
• The catalysts are chemoselective for nitrobenzene, styrene, and 3-nitrostyrene.
• The adsorption of nitro and vinyl groups depends on the catalyst surface properties.
• The carbon materials prepared can serve as metal free hydrogenation catalysts.

An activated carbon (AC) was treated by hydrogen peroxide and ammonia to dope oxygen and nitrogen on its surface. The surface-functionalized AC catalysts were used for the transfer reduction of nitrobenzene, styrene, and 3-nitrostyrene by hydrazine hydrate. The reduction of nitrobenzene and 3-nitrostyrene was promoted over the oxygen- and nitrogen-doped catalysts compared to the parent AC catalyst. Those were less active for the reduction of styrene but active for the reduction of vinyl group of 3-nitrostyrene. However, the nitrogen dopant suppressed the reduction of vinyl group of 3-vinylaniline. The functionalized AC catalysts are likely to facilitate the adsorption and activation of nitro group of the nitro substrates through interactions with polarized surface induced by the oxygen and nitrogen hetero dopants. This should make it possible to reduce the vinyl group of 3-nitrostyrene on the surface. The nitrogen dopant hindered the reduction of the vinyl group of 3-vinylaniline because the adsorption through its amino group should become difficult on the surface of basic nature induced by the nitrogen doping. The AC serves as an electrical conductor and its performance should be enhanced by the surface functionalization and this would contribute to the formation of reducing species such as diimide and proton from hydrazine on the surface. The present results show that oxygen- and/or nitrogen-doped, functionalized carbon materials could be promising as metal-free multi-task catalysts.

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