On the synthesis and adsorption properties of single-unit-cell hierarchical zeolites made by rotational intergrowths

The preparation of hierarchical zeolites usually involves hard or soft templates and multiple synthesis steps, which often prohibit their industrial uses. One way to overcome these issues is to build hierarchical zeolites using repetitive branching, where the intrinsic growth patterns of zeolites, instead of porogenic templates, are utilized. This paper expands on an earlier report to unravel the sequence of events leading to this repetitive branching process for the framework type MFI zeolite structure using small-angle X-ray scattering and transmission electron microscopy. Moreover, adsorption and transport properties of the hierarchical zeolite are probed using 2,2-dimethylbutane, n-hexane, and n-nonane. Self-pillared pentasil (SPP), a hierarchical zeolite, is formed by rotational intergrowth of MFI structures and MEL structures: the higher-symmetry structure (MEL, blue) serves as a connector to connect the lower-symmetry structure (MFI, red). This process is repeated over space and time, to achieve the formation of this all-crystalline hierarchical zeolite.