Sandwich-Type Zeolite Intergrowths with MFI and the Novel Extra-Large Pore IDM-1 as Ordered End-Members

Abstract

Stacking faults are two-dimensional planar defects frequently arising in zeolites, modifying their properties and potentially affecting their performance in catalysis and separation applications. In classical zeolite intergrowths, a topologically unique zeolite layer may often pile up after some spatial transformation (lateral translation, rotation, and/or reflection) that may occur in different amounts or directions with about similar probabilities, leading to a difficult to control disorder. Here, we present a new kind of zeolite intergrowth that requires an additional topologically distinct layer rather than a spatial transformation of a unique one. Stacking of the so-called pentasil layers produces the well-known medium pore zeolite MFI. Intercalation in strict alternation of a topologically distinct second layer sandwiched between pentasil layers expands the structure to produce the new extra-large pore IDM-1. Stacking disorder modulates the structural expansion along the stacking direction. The disordered materials have been studied by simulation of the X-ray diffraction patterns using the program DIFFaX and by Cs-corrected high-resolution electron microscopy. We show that disorder does not occur at random but in extended domains and can be controlled all the way from MFI to IDM-1 by just varying the concentration of the synthesis mixture.

Direct synthesis of IDM-1 aluminosilicate nanosheets with improved MTP performance

“…2B), characteristic of the typical structure of IDM-1 silicate. 14 Moreover, as the Al-I1 nanosheets became thinner, the b -axis-related diffraction peaks ((020), (011), (111), and (040)) decreased in relative intensity and became broadened (Fig. 2B).…”

Synthesis and Crystal Growth Mechanism of PST-2: An Aluminosilicate SBS/SBT Zeolite Intergrowth

“…To date, controlling the intergrowth rate in zeolites has been commonly achieved using a mixture of two OSDAs in various proportions ( e . g ., MFI/MEL and FAU/EMT), changing the water content in synthesis mixtures and the crystallization temperature (STF/SFF and MFI/IDM-1), ,− or by modifying the size/shape of a particular biselective OSDA (CHA/AEI) . To date, however, there are no reports regarding the crystallization time dependence of the intergrowth rate in zeolites as observed here.…”

Intergrowth Zeolites, Synthesis, Characterization, and Catalysis

“…It remains to be noted that intergrowth zeolites are not preferred by academia and industry at present, so more effort and research into this exciting material is highly recommended. Over the next few years, strategies for the synthesis of novel intergrowth zeolites, whether it be the exploitation and coordination of OSDA or the use of computational techniques to predict directed synthesis, will be the subject of ongoing research and debate . In addition, there are some fascinating ideas based on the unproven intergrowth structure that are gradually gaining recognition.…”

“…Over the next few years, strategies for the synthesis of novel intergrowth zeolites, whether it be the exploitation and coordination of OSDA or the use of computational techniques to predict directed synthesis, will be the subject of ongoing research and debate. 26 In addition, there are some fascinating ideas based on the unproven intergrowth structure that are gradually gaining recognition. Intergrowth zeolites have one or more phase boundaries, and the directional construction of these "heterojunctions" endows the crystals with new diffusion pores and channels.…”

“…The synthesis of zeolites is a complex and interesting process involving a variety of factors, such as the type of raw material, the initial gel ratio, the design of the structure directing agent (SDA), the time and temperature of crystallization, etc. To date, a variety of strategies have been developed for the synthesis of intergrowth zeolites, such as the use of SDA, F, and hydrothermal media-based seeds, similar to the pure-phase zeolite. − Table lists all the intergrowth zeolites that have been synthesized. At least three points need to be considered when designing intergrowth catalysts for the synthesis of specific catalytic reactions: (1) Design organic structure-directing agents (OSDAs).…”