Pd-Supported N/S-Codoped Graphene-Like Carbons Boost Quinoline Hydrogenation Activity

Pd nanoparticles (similar to 2.1 nm) supported on biomolecule-derived graphene-like carbons have been studied as highly active and stable catalysts for the selective hydrogenation of quinolines. A novel strategy is developed by pyrolysis of guanine with H2SO4, yielding heteroatom-doped (N/O, N/O/S) and minimally layered carbon nanosheets with large accessible areas, which can facilitate mass transfer and stabilize Pd nanoparticles. XPS results indicate that the intensity ratio of Pd-0/Pd2+ increases with N/S codoping in graphene-like carbons, suggesting a significant correlation between support properties and electronic structure of Pd species. N/O/S-codoped Pd@GS1000 shows substantially enhanced activity for quinoline hydrogenation reactions, with almost >99% conversion and >99% selectivity to 1,2,3,4-tetrahydroquinoline under mild catalytic conditions, superior to Pd@G1000 (without sulfur doping) and the reference Pd/OCNT catalyst. Further investigation indicates that sulfur containing carbon nanosheets strongly interact with metal supports, and thus metallic Pd can be regarded as an active center for hydrogenation reactions. This work may provide a framework for the development of promising applications of supported catalysts based on ultrathin carbon nanosheets in fine chemical production.