Liquid-phase catalysis by single-size palladium nanoclusters supported on strontium titanate: Size-specific catalysts for Suzuki-Miyaura coupling

Metal nanoclusters comprising several to tens of atoms are strong candidates for advanced catalysis as they are highly size-specific, with unique chemical properties, which were revealed by gas-phase molecular beam experiments. The size-specificity of nanoclusters makes them potentially suitable for fabricating tailor-made catalysts optimized by chemical composition as well as size parameters. To exploit their full catalytic potential, complete understanding of size specificity in catalysis under realistic reaction conditions is essential, together with a suitable method for fabricating single-size nanocluster catalysts. We have demonstrated herein aqueous-phase catalysis by single-size palladium nanoclusters supported on a well-defined strontium titanate surface for the Suzuki-Miyaura coupling reaction, showing that a 13-mer exhibits highly size-specific activity, as well as a general increase in catalytic activity as the nanocluster size decreases. By comparison with the reactivity of heteroatom doped nanoclusters, the relationship between the size-specific activity and site-specific charge distribution is revealed by evaluating electronic structures using X-ray photoelectron spectroscopy.