Pd⁰-polyoxometalates cluster–cluster catalyst for efficient selective hydrogenation of olefins

Clusters exhibit unique activity and selectivity in catalysis. However, research on the interactions between clusters and their synergistic catalysis is still in its infancy. Herein, ultrafine sub-nanowires composed of Pd⁰ sub-nanoclusters and polyoxometalates (POMs) stacked by cluster–cluster are successfully constructed (abbreviated as Pd-POMs). Notably, Pd-PW₁₂ exhibits exceptional activity (99%) and selectivity (99%) for the hydrogenation of C=C bonds in 4-vinylbenzaldehyde, significantly outperforming other supported Pd-based catalysts. Density functional theory (DFT) calculation results indicate that POMs can stabilize and adjust the electronic structure of Pd clusters, promoting the specific adsorption and reducing hydrogenation energy barriers of C=C bonds. Moreover, the electron–coupled proton (e⁻/H⁺) transfer process at the interface can be regulated by altering the redox properties of POMs, achieving extra regulations of the catalytic activity. This work reveals the synergistic optimization effects of POMs on the activity and selectivity of Pd clusters, providing new insights into the rational design of highly efficient catalysts.