Engineering ultrafine Pd clusters on laminar polyamide: A promising catalyst for benzyl alcohol oxidation under air in water

Polymer supports play an important role in noble metal loaded catalysts. In this study, palladium clusters stabilized by several polyamides have been widely studied in the oxidation of benzyl alcohol under airflow. The different kinds of polyamides (PADs) were synthesized with aromatic diamines and trimesoyl chloride by mechanical grinding method and solvent-heat method. Polyamide support was synthesized through mechanical grinding method. And the laminar structure and abundant amide bonds of polyamide can help obtain ultrafine Pd clusters with a mean particle size of 1.76 nm. The Pd 0.5 @PAD-2-M effectively catalyzed benzyl alcohol into benzaldehyde with a conversion of 96.1 % and turnover number (TON) of 1441 under 90 °C in water which was 2.5 times higher than the commercial Pd/C catalyst. High TON value of 6505 was also achieved in solvent-free system. This work reveals the advantages of laminar structure of polyamide in dispersing Pd clusters and promoting benzyl alcohol conversion. Besides, the carrier properties of amphipathy and substrate adsorption were also investigated to illustrate the significance of interfacial effect for laminar catalyst in heterogeneous catalysis.