Room-Temperature Tandem Condensation-Hydrogenation Catalyzed by Porous C3N4 Nanosheet-Supported Pd Nanoparticles

Tandem catalysis, often inspired by biological systems, offers many advantages in the synthesis of highly functionalized small molecules. NH2-grafted porous C3N4 nanosheet with rich N species and surface area of 138 m(2)/g was fabricated via a NH3-exfoliation method. After supporting Pd nanoparticles, the resulting bifunctional catalyst (Pd/C3N4-NH2) could catalyze a one-step tandem condensation-hydrogenation reaction between ketones and nitriles to form alpha-alkylated nitriles at room temperature. Under 2 MPa H-2 for 8 h, Pd/C3N4-NH2 could afford 99.7% cyclohexanone conversion and 99.8% selectivity without other side reactions, which is much higher than that of bulk C3N4-supported Pd. Compared with commonly used two-step processes, this one-step tandem reaction could largely shorten reaction time and allow condensation-hydrogenation to take place at room temperature. We also found that the hydrogenation step accelerated the condensation step, which increased the overall efficiency of the tandem transformation. This catalytic system demonstrates the design of a bifunctional catalyst with cooperative sites that allow the tandem reaction to take place in one step under mild conditions.