Inorganic solids with hierarchical open-structures have offered opportunities for the design of new heterogeneous catalysts that could contain spatially accessible, structurally well-defined and -separated active centers. Generally, hierarchical pore structures refer to pores of different sizes that are uniformly distributed over a whole particle. Recently, porous solids with core–shell structures have gradually triggered a great deal of research interest due to their unique and well-arranged bimodal-pore structures and potential applications in adsorption, separation, catalysis, biomedicine, etc.

Prof. Dongyuan Zhao’s group has successfully synthesized the uniform core–shell composites with cage-like mesoporous silica shells and zeolite cores by a reproducible acid-catalyzed sol–gel process. The cage-like mesoporous silica shells are continuously covered on each zeolite microcrystal, and the shell thicknesses can be controllably tuned in the range of 25–70 nm by adjusting the synthetic conditions. The core–shell composite possesses a high surface area (~862 m2 g-1), external pore volume (~0.66 cm3 g-1) and large pore sizes (3.2–8.2 nm). The direct and tight connection between cage-like mesoporous silica shells and zeolite cores results in highly open and stable hierarchical micro/mesopore frameworks. Uniform Pt nanocatalysts (~3.2 nm) can be introduced and well-dispersed into the core–shell composite. The Pt/HZ@CmesoSiO2 composites show excellent catalytic activity and durability for the catalytic oxidation of toluene (J. Mater. Chem. A, 2013, DOI: 10.1039/C3TA10992E).