Palladium Nanoparticles Anchored on COFs Prepared by Simple Calcination for Phenol Hydrogenation

Covalent organic frameworks (COFs) used as supports for metal nanoparticles (MNPs) show high efficiency in heterogeneous catalysis. Developing a green and efficient way to synthesize COFs remains a great challenge. Herein, an imine COF (TpPa-1) was prepared via a green and convenient calcination method under low temperature, and then Pd nanoparticles (NPs) were loaded to prepare Pd@COFs catalysts for the selective phenol hydrogenation to cyclohexanone. XRD and FTIR results confirm the successful synthesis of TpPa-1 by a simple calcination method. A suitable calcination temperature (280 °C) is conducive to the synthesis of TpPa-1 (COF-280) with higher crystallinity, larger BET surface area, higher mesoporous proportion, and uniform spherical morphology. These characteristics of COF-280 increase the Pd loading, promote the formation of Pd with higher Pd0 proportion on the catalyst surface, and enhance the mass transfer, thereby improving the catalytic properties of Pd@COF-280 for the phenol hydrogenation, with a catalytic activity increased by 2 times compared to Pd@COF-220. The addition of p-toluenesulfonamide during the synthesis can affect the crystallinity and morphology of TpPa-1 and the corresponding catalytic performance. Furthermore, Pd@COF-280 shows good reusability during four reaction cycles. The work provides a green approach for preparing imine-COFs and their efficient applications in heterogeneous catalysis.