In Situ Imaging of Silicalite-1 Surface Growth Reveals the Mechanism of Crystallization

Abstract

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. Using time-resolved atomic force microscopy images, we observed silica precursor attachment to crystal surfaces, followed by concomitant structural rearrangement and three-dimensional growth by accretion of silica molecules. We confirm that silicalite-1 growth occurs via the addition of both silica molecules and precursors, bridging classical and nonclassical mechanisms.

Mechanistic Insights into Growth of Surface‐Mounted Metal‐Organic Framework Films Resolved by Infrared (Nano‐) Spectroscopy

“…This band is present in fully reacted mixtures of Cu−btc (Figure 2 c), and also for the films grown with drying each whole cycle (Figure 2 a); the vibration at 1620 cm −1 (mode v 2 ) is prominent for the hindered‐grown films (Figure 3 c) and belongs to COO − (from Cu−btc) in the partially exchanged [Cu 2 Ac 2 (btc) 2 ]; similarly, the band at 1550 cm −1 (mode v 4 ) likely belongs to the COO − (from Cu−Ac) vibrations in the partially exchanged [Cu 2 (btc) 2 Ac 2 ], whereas the band at around 1580 cm −1 (mode v 3 ) is attributed to an asymmetric COO − mode of [Cu 2 Ac 4 ], based on the IRRAS spectra of copper acetate (Figure 2 c). The arrangement and chemistry of these species could be responsible for the previously observed surface diffusion barriers and defects in [Cu 3 (btc) 2 ] films with unclear chemical origin 4, 33…”

“…To circumvent this limitation, we have complemented IRRAS results with tip‐sensed AFM‐IR microscopy approaches 30, 31a,31b. Apart from providing topological information of AFM as a powerful method to study mechanisms of crystal growth,32, 33 AFM‐IR can further provide local spectroscopic information with spatial resolution around 10 nm. Various versions of AFM‐based IR microscopy have been recently employed, including synchrotron‐based IR mapping of metal nanoparticle catalysis,34 structural analysis of μm‐sized MOF crystals35 and zeolite thin film investigations,31b but its application to study the initial stages of the SURMOF growth process with a monolayer chemical sensitivity has, to the best of our knowledge, never been demonstrated.…”

Lie, Santilli, and nanotechnology: From the elementary particles to the periodic table of the elements

“…In the kick-off primordial Universe the serpentine route to the Hydrogen atom that together with some Helium prevails there reminds of the "3D island growth…pathway of layered growth" recently described at "angstrom-scale [and even single-atom scale] resolution" 19,20 in surface crystallization processes, where "the growth units are individual molecules and ions that attach in monomolecular steps present on a crystal surface" (Ib.). That the same modus operandi with identical topographical "step heights, terrace widths, and other surface features" (Ib.)…”

“…7b) and there cyclically uncoiling under shedding off of photons and neutrinos and other fragments until in the ultimate end pairwise sandwiching up along the sides as a wafer of together equally many singlets as the cloud's amount. Maybe not so crystal-clear formulated -but clear for re-crystallization by the formation of so individualized Hydrogen ion seeds by cross-sectional extrusion in an alternating sequence from the here vertically duplicated Bohr-periodic singlet "terraces" 19,20 (Fig. 8a).…”

Exploring Zeolite Chemistry with the Tools of Surface Science: Challenges, Opportunities, and Limitations

“…Note also that we deal here with models for the interior of the zeolite pores, and not the outer surface of zeolite crystals. The external surface of zeolites has been studied for example by atomic force microscopy to significant level of detail such that now mechanisms of zeolite growth can be addressed using this strategy, 13 and even molecules on the surface of zeolite crystallites could be imaged 14 .…”