Tuning Zeolite Precursor Interactions by Switching the Valence of Polyamine Modifiers.

Nonclassical mechanisms of crystal growth often involve the formation of amorphous precursors that play a direct role in what is generally referred to as crystallization by particle attachment (or CPA). One of the most studied CPA systems in the literature is zeolite MFI, which is a microporous crystal with siliceous (silicalite-1) and aluminosilicate (ZSM-5) isostructures. The self-assembly, microstructural evolution, and mechanistic role of nanoparticle precursors (1-6 nm) during silicalite-1 crystallization have been the subjects of prior investigation by combined experimental and modeling techniques.

In situ imaging of silicalite-1 surface growth reveals the mechanism of crystallization.

The growth mechanism of silicalite-1 (MFI zeolite) is juxtaposed between classical models that postulate silica molecules as primary growth units and nonclassical pathways based on the aggregation of metastable silica nanoparticle precursors. Although experimental evidence gathered over the past two decades suggests that precursor attachment is the dominant pathway, direct validation of this hypothesis and the relative roles of molecular and precursor species has remained elusive. We present an in situ study of silicalite-1 crystallization at characteristic synthesis conditions.

A facile strategy to design zeolite L crystals with tunable morphology and surface architecture.

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.

Tailoring silicalite-1 crystal morphology with molecular modifiers.

Modified point of view: a bio-inspired approach was used to tailor silicalite-1 crystallization. Growth modifiers (ZGMs) with molecular recognition for binding to specific crystal faces produced drastic changes in zeolite crystal morphology. This facile approach offers an efficient method for tuning zeolite properties.