Exploring the Influence of Inter‐ and Intra‐crystal Diversity of Surface Barriers in Zeolites on Mass Transport by Using Super‐Resolution Microimaging of Time‐Resolved Guest Profiles

Abstract

The applications of nanoporous crystalline materials are closely related to the mass transfer of guest molecules. However, the fundamental knowledge of mass transfer, and in particular the surface barriers controlled by the permeation of guest molecules through the external surfaces of materials, is still incomplete. The diversity of surface permeability at the single-crystal level, caused by the varying origins of surface transport resistance, hinders the rational materials design and needs better understanding. Herein, we probe the molecular transport in single zeolite crystals with fluorescent 4-(4-diethylaminostyryl-1-methylpyridinium iodide) (DAMPI) using super-resolution structured illumination microscopy (SIM). It showed that both the inter-and intra-crystal diversity of surface barriers could be monitored by detecting the diffusion behaviors on the center and surface planes in single crystals. This adds a new perspective for studying the origins of the surface barriers as well as the molecular transport mechanisms in nanoporous materials.

Quantifying molecular surface barriers and intracrystalline diffusion in nanoporous materials by zero‐length column

“…In the work of Bonilla et al, 46 the surface permeability of ethane on SAPO-34 is measured as 5.67 Â 10 À7 m 2 /s, which is of the same order of magnitude as our results. Due to the diversity of surface barriers between crystals, 27,47 the surface permeability obtained by the macroscopic technology is the result of statistical average of multiple grains, which is speculated to be the reason for the difference in surface permeability measured by macroscopic and microscopic technique. Since the macroscopic method is still a better choice for measuring small-sized crystals with the industry interests (the requirements of optical testing methods for size of crystals are usually within $50 μm 26 ).…”