Hollow SAPO-34 Cubes with Hierarchically Organized Internal Structure

We herein report novel hollow SAPO-34 cubes with a hierarchical internal structure. They are prepared from dry gels containing gelatin by a vapor-phase transport method. Microscopic characterization reveals that the cubes are constructed by symmetrically packed four two-top-point truncated octahedrons encapsulated by dense crystalline shells, exhibiting a structure-in-structure formation. The cubes show either +-shaped or the butterfly like X-shaped black spots on their faces under light. Investigation of the formation process of the hollow SAPO-34 cubes demonstrates a surface to core crystal growth route, which has not been found in vapor-phase transport synthesis of zeolites. A possible formation mechanism is proposed.