A Facile Strategy To Design Zeolite L Crystals with
Tunable Morphology and Surface Architecture
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Abstract
Tailoring
the anisotropic growth rates of materials to achieve
desired structural outcomes is a pervasive challenge in synthetic
crystallization. Here we discuss a method to selectively control the
growth of zeolite crystals, which are used extensively in a wide range
of industrial applications. This facile method cooperatively tunes
crystal properties, such as morphology and surface architecture, through
the use of inexpensive, commercially available chemicals with specificity
for binding to crystallographic surfaces and mediating anisotropic
growth. We examined over 30 molecules as potential zeolite growth
modifiers (ZGMs) of zeolite L (LTL type) crystallization. ZGM efficacy
was quantified through a combination of macroscopic (bulk) and microscopic
(surface) investigations that identified modifiers capable of dramatically
altering the cylindrical morphology of LTL crystals. We demonstrate
an ability to tailor properties critical to zeolite performance, such
as external porous surface area, crystal shape, and pore length, which
can enhance sorbate accessibility to LTL pores, tune the supramolecular
organization of guest–host composites, and minimize the diffusion
path length, respectively. We report that a synergistic combination
of ZGMs and the judicious adjustment of synthesis parameters produce
LTL crystals with unique surface features, and a range of length-to-diameter
aspect ratios spanning 3 orders of magnitude. A systematic examination
of different ZGM structures and molecular compositions (i.e., hydrophobicity
and binding moieties) reveal interesting physicochemical properties
governing their efficacy and specificity. Results of this study suggest
this versatile strategy may prove applicable for a host of framework
types to produce unrivaled materials that have eluded more conventional
techniques