Heteroepitaxial growth of gold on flowerlike magnetite: An efficacious and magnetically recyclable catalyst for chemoselective hydrogenation of crotonaldehyde to crotyl alcohol

Au/Fe3O4 catalysts with flowerlike and particulate morphologies have been prepared by homogeneous deposition–precipitation of gold on hematite materials synthesized in different ways, followed by integrative reduction. HRTEM revealed the heteroepitaxial growth of gold crystallites on flowerlike magnetite materials along the {1 1 1} planes, which may account for their smaller and more uniform gold nanoparticles. The stronger metal-support interaction on flowerlike Au/Fe3O4 catalysts was also manifested by the higher reduction temperature of gold than that on particulate magnetite-supported catalysts. In liquid phase hydrogenation of crotonaldehyde, the flowerlike Au/Fe3O4 catalysts show high selectivity (⩾76%) in the entire reaction course and high yield (⩾75%) to crotyl alcohol. They also display excellent separation and recycling characteristics. A perimeter interface mechanism involving the hydroxyl groups on magnetite and the positively charged gold atoms linked to the lattice oxygen of magnetite is established to address the remarkably high selectivity over the flowerlike Au/Fe3O4 catalysts.