Covalently and non-covalently immobilized clusters onto nanocarbons as catalysts precursors for cinnamaldehyde selective hydrogenation

• Ru mixed nanoparticles were prepared on carbon nanotubes and graphene from clusters.
• The cluster ligands allow covalent or non-covalent π–π interactions with carbon.
• Activity/selectivity in cinnamaldehyde hydrogenation is influenced by particle size.
• Selectivity is shifted from cinnamyl alcohol to hydrocinnamaldehyde by changing solvent.
• The best catalysts gave high selectivity in cinnamyl alcohol and could be reused.

Ru-based nanoparticles were deposited on carbon nanotubes and graphene via an organometallic approach involving mixed-metal clusters modified with appropriate ligands. These ligands allowed either covalent or non-covalent π–π interactions with the carbonaceous surfaces. The immobilized clusters were then coalesced at different temperatures to give carbon-supported nanoparticles of different sizes. The obtained catalysts were tested in the selective hydrogenation of cinnamaldehyde. It was found that the nature of the metal(s), support nature, incorporation method and activation temperature all had a profound influence on activity and selectivity. Interestingly, the selectivity could be shifted from cinnamyl alcohol (COL) to hydrocinnamaldehyde (HCAL) by changing the reaction solvent. The best catalysts gave a very high selectivity in cinnamyl alcohol, which is not the more thermodynamically favored product, and could be reused several times without loss of activity or selectivity.

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