Hierarchical TiO2 microspheres supported ultrasmall palladium Nanocrystals: A highly efficient catalyst for Suzuki reaction

A hierarchical titanium dioxide microspheres-supported palladium catalyst (Pd/TiO2-350) was prepared and characterized using BET, XRD, XPS, SEM, EDX, and TEM analyses. An ICP-OES analysis of Pd/TiO2-350 further confirmed the successful Pd immobilization on TiO2 with a palladium loading of 0.1 mmol g−1. Pd/TiO2-350 efficiently catalyzed the Suzuki-Miyaura reaction of aryl iodides with arylboronic acids to give the corresponding biaryl derivatives in good to excellent yields. After the reaction, the catalyst was recovered by centrifugation and reused three times without significant loss of its catalytic activity. Moreover, the loading of palladium species further decreased to 0.001 mol%, and the total turnover number and turnover frequency of the catalyst reached as high as 99 000 and 0.57 s−1, respectively.