Synthesis and catalytic activity of palladium supported on heteroatom doped single-wall carbon nanohorns

The dehydrogenation of indoline to indole is a vital chemical transformation because of the versatile application of indole as an intermediate in the synthesis of medicines or fine chemicals. As a consequence, various approaches are being explored to catalyze dehydrogenation of indoline. Here, we provided a new strategy for dehydrogenation of indoline. Pd nanoparticles supported on boron-, oxygen-, nitrogen- and phosphorus-doped single-wall carbon nanohorns (CNHs) without ligands were synthesized via a one-step ultrasonic method. Pd nanoparticles with a diameter of 2–3 nm were dispersed uniformly on heteroatom-doped CNHs. The as-prepared Pd-OCNHs (Pd nanoparticles supported on oxygen-doped CNHs) exhibited excellent performance as the catalyst in dehydrogenation of indoline at a low temperature due to a synergistic effect between metal palladium and oxygen-doped CNHs (OCNHs). In the process, metal palladium offers the main active site for adsorption of indoline, and OCNHs not only act as a carrier, but also provide the active groups (ketonic CO) for C–H activation of reactants to improve the catalytic activity. Pd-OCNHs could open up a novel way to the dehydrogenation of other heterocycles.