Vapour-phase-transport rearrangement technique for the synthesis of new zeolites

Abstract

Owing to the significant difference in the numbers of simulated and experimentally feasible zeolite structures, several alternative strategies have been developed for zeolite synthesis. Despite their rationality and originality, most of these techniques are based on trial-and-error, which makes it difficult to predict the structure of new materials. Assembly-Disassembly-Organization-Reassembly (ADOR) method overcoming this limitation was successfully applied to a limited number of structures with relatively stable crystalline layers (UTL, UOV, *CTH). Here, we report a straightforward, vapour-phase-transport strategy for the transformation of IWW zeolite with low-density silica layers connected by labile Ge-rich units into material with new topology. In situ XRD and XANES studies on the mechanism of IWW rearrangement reveal an unusual structural distortion-reconstruction of the framework throughout the process. Therefore, our findings provide a step forward towards engineering nanoporous materials and increasing the number of zeolites available for future applications.

Zeolite (In)Stability under Aqueous or Steaming Conditions

“…[ 121 ] Further reduction in l/z ratio, UTL hydrolysis under vapor‐phase‐transport conditions, led to the formation of IPC‐7P with alternating s4r and d4r interlayer bridges. [ 125 ] Hydrolysis of germanosilicates is a rather complex process with multiple outcomes, strongly dependent on the reaction conditions, as is summarized for UTL in Figure 8. More details on the potential of the assembly‐disassembly‐organisation‐reassembly synthesis, [ 1d ] based on the transformation of germanosilicates via partial hydrolysis into new zeolite structures, can be found elsewhere.…”

Mechanochemically assisted hydrolysis in the ADOR process

“…Depending on the actual 2q value, conclusions about the nature of the linkages are possible. 22 Zeolites with frameworks IWR, 24 IWW, 25,26 UOV, 27,28 and *CTH 29 exhibit similar structural features as UTL in that they contain d4r units, and have been successfully used in the ADOR process to produce a variety of new frameworks. There are still more frameworks to explore, such as zeolite IWV, 30,31 which also contain the necessary structural features required for ADOR.…”

Water‐Induced Structural Dynamic Process in Molecular Sieves under Mild Hydrothermal Conditions: Ship‐in‐a‐Bottle Strategy for Acidity Identification and Catalyst Modification

“…[9,10,15,16] This process includes two critical steps: (1) the generation of the building units and (2) the self-assembly of these units.W ater is an essential substance for the successful synthesis and has the following functions:working as reaction medium, determining the extent of hydrolysis, accelerating the condensation reactions and modulating the crystallization kinetics. [17][18][19] Besides the necessity for hydrothermal synthesis,water vapor or steam also play asignificant role in post-treatment for molecular sieves modification. High-temperature (> 600 8 8C) steaming is often used for dealumination to construct hierarchical porosity,reduce acid density and improve the hydrothermal stability of molecular sieves (Scheme 1a).…”