Size-Controllable Palladium Nanoparticles:  Superior Catalytic Activities Over Identically Ligated Tri-Palladium Clusters

Abstract

Small-sized palladium nanoparticles (PdNPs) are highly active nanocatalysts and have attracted great interest for many years. However, preparing size-controllable PdNPs is still challenging. Here, ultrafine air-stable PdNPs-1/2 (2.0 ± 0.3 nm/1.2 ± 0.4 nm) stabilized by multiple nucleophilic ligands (phosphines, thiols and anions) were prepared, and their sizes could be successfully regulated by simply varying anionic ligands (SbF6- or BF4-). We further investigated their catalytic activities and compared them with their identically ligated tri-palladium clusters [Pd3]+-1/2. These size-controllable PdNPs presented superior catalytic activities for both the Suzuki-Miyaura cross-coupling (SMCC) and the 4-nitrophenol reduction reactions. The PdNPs-1 exhibited the highest catalytic activity for both reactions with good applicability to different substrates and the reaction rate constant reached 1.10 × 10-2 S-1 for the 4-nitrophenol reduction. These results revealed that the employment of different anionic ligands significantly affects the size of PdNPs and their synergistic catalytic activities. This work will open multiple possibilities for preparing ultrafine PdNPs with controllable size, good dispersity and stability for a broad range of applications.

Keywords: Size-Controllable Palladium Nanoparticle, Tri-palladium Clusters, SMCC Reaction, Nitrophenol Reduction