日本ゼオライト学会　刊行物 Publication of Japan Zeolite Association

Hollow silica spheres possessing void space from tens to hundreds of nanometers in size can be used as a platform material for the design of advanced heterogeneous catalysts, because the enclosed void space is expected to be useful for encapsulation and compartmentation of active catalytic components, and the outer silica shell acts as a physical barrier to protect them from leaching and aggregation or endow them with a molecular sieving property. Although a number of strategies have been developed for the synthesis of hollow silica structures encapsulating catalytic components such as metal oxides and metal nanoparticles in their internal void spaces （so-called “yolk–shell” structures）, most of them requires complex multiple synthetic procedures. We have recently developed several methodologies for the synthesis of yolk–shell structured catalysts by using O/W microemulsions or aminopolymers as templates. In this review, the synthesis of hollow silica structures containing TiO₂ particles or Pd nanoparticles as catalytically active species and their catalytic applications are described.