Palladium Nanoparticles Anchored on COFs Prepared by Simple Calcination for Phenol Hydrogenation
Hong Jiang, Xinhui Shen, Fengnan Wang, Jiuxuan Zhang, Yan Du, Rizhi Chen
Abstract
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.