Efficient catalysis of Pd (II) supported by thiourea covalent organic framework in Suzuki coupling reaction

Abstract

Covalent organic frameworks (COFs) were ideal carriers for noble metal catalysts due to their rich pore structure, pre-designable monomers, and high stability. Herein, a series of novel thiourea-based COFs (Tx-COFs) enriched with heteroatoms were constructed to provide abundant and powerful anchoring sites for metal. The successful preparation of Pd@COFs with high metal dispersion and substantial active sites was confirmed by XPS and STEM-EDX element mapping. These catalysts exhibited excellent catalytic activity and stability for the Suzuki-Miyaura coupling reaction. Especially for Pd@TU-COF, the catalyst still catalyzed the reaction at room temperature to afford the product in a yield of 99 % after 10 reuses, while the palladium load only decreased from 5.78 % to 5.66 %. The structure-activity relationships between the metal loading mode, the structure of Tx-COF, and its catalytic performance were also investigated in this study, which provided a feasible strategy for the preparation of efficient and stable heterogeneous catalysts.