Porosity Control of Pd@SiO₂ Yolk–Shell Nanocatalysts by the Formation of NickelPhyllosilicate and Its Influence on Suzuki Coupling Reactions

다국어 초록 (Multilingual Abstract)

<P>The surface of Pd@SiO<SUB>2</SUB> core–shell nanoparticles(<B>1</B>) was simply modified by the formation of nickel phyllosilicate.The addition of nickel salts formed branched nickel phyllosilicatesand generated pores in the silica shells, yielding Pd@SiO<SUB>2</SUB>–Niphy nanoparticles (Niphy = nickel phyllosilicate; <B>2</B>, <B>3</B>). By removal of the silica residue, Pd@Niphyyolk–shell nanoparticles (<B>4</B>) was uniformly obtained.The four distinct nanostructures (<B>1</B>–<B>4</B>) were employed as catalysts for Suzuki coupling reactions with arylbromide and phenylboronic acid, and the conversion yields were inthe order of <B>1</B> < <B>2</B> < <B>3</B> < <B>4</B> as the pore volume and surface area of the catalystsincreased. The reaction rates were strongly correlated with shellporosity and surface exposure of the metal cores. The chemical inertnessof nickel phyllosilicate under the basic conditions rendered the catalystsreusable for more than five times without loss of activity.</P><P><B>Graphic Abstract</B>
<IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/langd5/2012/langd5.2012.28.issue-15/la300148e/production/images/medium/la-2012-00148e_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/la300148e'>ACS Electronic Supporting Info</A></P>