(96g) Synthesis of Single-Unit-Cell Hierarchical Zeolites with Tunable Mesoporosity By Controlling Intergrowth Frequency

The introduction of mesoporosity in microporous zeolites is advantageous for certain catalytic applications by providing improved accessibility to active sites through reduction of diffusion limitations. A single-unit-cell hierarchical (meso/microporous) zeolite, known as self-pillared-pentasil zeolite (SPP) (1, 2) can be made by direct one-step synthesis based on a crystal growth phenomenon known as twinning. The mesoporosity between the single-unit-cell thick branches of SPP is created through repetitive 90° rotational intergrowths of MFI nanosheets. In principle, the mesopore size can be controlled by the frequency of these rotational intergrowths. Here, we report such a controllable synthesis of SPP without using any surfactants or hard templates. A systematic shift of mesopore size distribution is observed by argon adsorption isotherms with variation of synthesis conditions. This more open structure of SPP allowed improved imaging by electron microscopy to elucidate the structure of the rotational intergrowth. Implications for catalysis and adsorption applications will be discussed.

References

1. Zhang, X. et al. Synthesis of Self-Pillared Zeolite Nanosheets by Repetitive Branching. Science 336, 1684 (2012).

2. Xu, D. et al. On the Synthesis and Adsorption Properties of Single-Unit-Cell Hierarchical Zeolites Made by Rotational Intergrowths. Adv. Funct. Mater. 24, 201–208 (2014).