Highly dispersed palladium nanoclusters anchored on nanostructured hafnium(iv) oxide as highly efficient catalysts for the Suzuki-Miyaura coupling reaction

High-efficiency and durable palladium (Pd)-based catalysts are desirable for the Suzuki-Miyaura coupling reaction, which is an efficient strategy for the construction of value-added carbon-carbon bonds in synthetic organic chemistry. Herein, we report the fabrication of highly dispersed Pd nanoclusters anchored on nanostructured hafnium(iv) oxide (HfO2; Pd@HfO2) catalysts via the two-step pyrolysis of a Hf-based metal-organic framework precursor in the presence of nitrogen and air, respectively. The resulting Pd@HfO2 catalyst presents excellent catalytic activity (>99%) for the cross-coupling of bromobenzene and phenylboronic acid, outperforming the analog Pd@ZrO2 (72%), as well as Pd/HfO2(Im) (90%) prepared via an impregnation method. This outcome was likely related to the highly dispersed ultra-small Pd nanoclusters and an appropriate number of acidic sites available within the HfO2 support. The Pd@HfO2 can be reused for at least 10 cycles without any decay in its catalytic reactivity. Moreover, the catalyst is also highly efficient for catalyzing the cross-coupling of phenylboronic acid and aryl halide with various functional groups, indicating its significant potential for industrial application.