Fractal MTW Zeolite Crystals: Hidden Dimensions in Nanoporous Materials

Abstract

Screw dislocation structures in crystals are an origin of symmetry breaking in a wide range of dense-phase crystals. Preparation of such analogous structures in framework-phase crystals is of great importance in zeolites but is still a challenge. On the basis of crystal-structure solving and model building, it was found that the two specific intergrowths in MTW zeolite produce this complex fractal and spiral structure. With the structurally determined parameters (spiral pitch h, screw angle θ, and spatial angle ψ) of Burgers circuit, the screw dislocation structure can be constructed by two different dimensional intergrowth sections. Thus the reported complexity of various dimensions in diverse crystals can be unified.

Unraveling the Twin and Tunability of the Crystal Domain Sizes in the Medium‐Pore Zeolite ZSM‐57 by Electron Crystallography

“…The presence of twin domains changes the straight 8‐ring channel to a “V‐shaped” structure in the bc plane of the MFS framework (Figure c). In contrast to the intergrowth of zeolite X/A and the MTW ‐type zeolite, no novel second building units on the twin boundary in the MFS ‐type zeolite can be found.…”

“…This phenomenon, frequently observed in the *BEA , *‐ITN , *MRE , *SSO , and *STO zeolite families, has been extensively investigated . Very recently, the overlap of an independent crystal twin and stacking disorder in the MTW ‐type zeolite along different dimensions derived an extremely complex fractal structure . Moreover, the rotational or epitaxial intergrowth of structurally related zeolites such as MFI / MEL and FAU / EMT will result in novel hierarchical zeolite architectures.…”

“…On one hand,m any endeavorsh ave been devoted to synthesizing new zeolitesw ith fascinating topologies, thereby enriching zeolite structural diversity.O ntheo ther hand, tailoringt he morphologies of knownz eolites for desirable catalytic properties by tuning twin domains, stacking disorders,a nd rotational or epitaxial intergrowth has received increasing attention in academic science and industry. [2][3][4] Crystal twinning occurs when separated crystals with the same crystallographic structure join by such symmetryo perations as the mirror plane,rotationaxis, or inversion center. For instance,m ulti-twinning components with pyramidalb oundaries in the ZSM-5 zeolite (FTC: MFI)h ave been uncovered by the electron backscatter diffraction (EBSD) method.…”

“…[7][8][9][10][11][12][13][14] Very recently,t he overlap of an independent crystal twin and stackingd isorder in the MTW-type zeolite along different dimensions derived an extremelyc omplex fractal structure. [2,15] Moreover,t he rotational or epitaxial intergrowth of structurally related zeolites such as MFI/MEL and FAU/EMT will resulti nn ovel hierarchical zeolite architectures.For example, the MEL and EMT nanodomains embedded in the MFI and FAU nanoflakes inducet he self-pillared zeolite sheet and house-of-cards nanosheet structures, respectively. [16][17][18] Probing these structuralf eatures at the atomic level will shed light on the mechanism of crystal growth and structure-activity relationships.…”

Ultrasonic Transducers Shaped in Archimedean and Fibonacci Spiral: A Comparison

“…Spiral geometries have been observed in nature, from small living systems such as snails, to big phenomena such as hurricanes, and even in the case of the crystal growth of nanostructured zeolites [25][26][27][28]. In the macro world, the mammalian cochlea is a very common natural evidence of spiral coiling, and the Archimedean and Fibonacci spirals are the nonlinear curves often used for its description [19,20].…”