Structured carbon felt with chemical functionalization as Pd catalyst support for selective hydrogenation of cinnamaldehyde.

[Display omitted] • Structured catalyst consisting of N doped carbon felt supported Pd NPs. • Surface oxygenated groups for introducing amine precursors of N dopants on carbon. • Pdδ+ interface between Pd NPs and carbon surface induced by coordination of pyridinic N to Pd precursors. • C=C bond hydrogenation enhanced by nonpolar surface and small NPs with high content of Pdδ+. • Easy recyclability for liquid-phase reaction due to monolith Pd/carbon catalyst. In this contribution, structured carbon tailored with various surface oxygen and nitrogen functionalities was synthesized using commercial carbon felt and further employed as support for Pd nanoparticles (NPs) in liquid-phase hydrogenation of α, β-unsaturated cinnamaldehyde. The surface oxygenated groups, generated by vapor acid treatment, play the role of exchange site for the selective introduction of the nitrogen-containing functional groups on the carbon support during amination step. The amine-group precursors can be converted into nitrogen-doping species after a high temperature annealing process. Such surface functionalized sites are actively involved in the metal-support interaction and provide anchoring sites for Pd NPs, thereby improving the hydrogenation activity and stability. We have found that the pyridinic N dopants coordinated by divalent Pd precursors along with charge transfer induce the formation of the partial positively charged Pdδ+ species on the metal NPs during reduction, consistent with the chemical shift observed in the N1s core level of N-doped carbon support. The trend of catalytic selectivity towards hydrocinnamaldehyde is closely correlated with the electronic structure of the active metal phase in addition to the particle size. Finally, the macroscopic shape of the carbon support enables an easy recovery of the catalyst from the liquid-phase media, hereby providing a strategy for the rational design of the monolith carbon supported catalysts. [ABSTRACT FROM AUTHOR]