Pyrene-Thiol-modified Pd Nanoparticles on Carbon Support: Kinetic Control by Steric Hinderance and Improved Stability by the Catalyst-Support Interaction

Aerobic oxidative dehydrogenation of amines to imines by thiol-modified Pd nanoparticle (NP) catalysts on carbon supports is reported herein. Whereas conventional non-modified Pd NP catalysts are nearly inactive, the carbon-supported Pd catalysts modified with thiol ligands efficiently catalyze the reaction with high selectivity. Kinetic studies and DFT calculations reveal that the rate-limiting imine product desorption step is significantly boosted on the thiol ligands-modified Pd surface compared to the non-modified Pd surface due to the steric hindrance of the ligands. Furthermore, the catalytic activity is dramatically enhanced in the presence of both pyrene-functionalized thiol modifiers and graphene-based carbon supports; 96 % conversion is attained after 4 h at 110 °C. The π–π interactions between pyrene groups and the highly crystallized carbon surface suppress the leaching of ligands, which offers improved catalyst stability even under O₂ atmosphere at 110 °C, thereby resulting in high activity.