Construction of Single‐Crystalline Hierarchical ZSM‐5 with Open Nanoarchitectures via Anisotropic‐Kinetics Transformation for the Methanol‐to‐Hydrocarbons Reaction

Abstract

We report an anisotropic‐kinetics transformation strategy to prepare single‐crystalline aluminosilicate MFI zeolites (ZSM‐5) with highly open nanoarchitectures and hierarchical porosities. The methodology relies on the cooperative effect of in situ etching and recrystallization on the evolution of pure‐silica MFI zeolite (silicalite‐1) nanotemplates under hydrothermal conditions. The strategy enables a controllable preparation of ZSM‐5 nanostructures with diverse open geometries by tuning the relative rate difference between etching and recrystallization processes. Meanwhile, it can also be extended to synthesize other heteroatom‐substituted MFI zeolite nanocages. Compared with conventional ZSM‐5 microcrystals, nanocrystals, and nanoboxes, the ZSM‐5 nanocages with single‐crystalline nature, highly open nanoarchitectures, and hierarchical porosities exhibit remarkably enhanced catalytic lifetime and low coking rate in the methanol‐to‐hydrocarbons (MTH) reaction.

Defect-Guided Synthesis of Hierarchical Sn-B-Beta Zeolite with Highly Exposed Sn Sites

“…Chemical etching has been documented to be a facile and efficient approach for introducing mesopores, which are conducive for exposing more active sites. − The basic organic structure directing agent (OSDA) can be used as etching agent for desilication to create mesopores. , On the other hand, the OSDA can also serve as template for assembling the building units into the zeolite structure. ,, Therefore, the dual-functional OSDA holds the promise to incorporate Lewis acid heteroatoms during constructing the mesoporous structure through an etching-regrowth route. , The consistent practice of etching is based on open channel zeolites in order to generate mesopores effectively. − This means installation of heteroatoms will be spatially uncontrollable, located on both intracrystalline micropores and the newly formed mesoporous domain. Thinking in another way, if the OSDAs remain occluded in the micropores, the heteroatoms would be hindered from entering the occupied micropores.…”

Facile and fast synthesis of highly active Lewis acid MWW zeolite from pure silica ITQ-1

“…27,28 Then, a part of the nest-form defects will be either healed by the migrated Si species or the newly introduced Sn species. 27,29 This assumption is further verified by N 2 gas physisorption and TEM imaging. Fig.…”

“…This is reasonable owing to the common etching effect of the basic SDA. 29,30 The TEM images of Si-MWW (Fig. 2a) and Sn-MWW-250 (Fig.…”

Regioselective Surface Assembly of Mesoporous Carbon on Zeolites Creating Anisotropic Wettability for Biphasic Interface Catalysis

“…The rational assembly and integration, from different porous functional moieties, into hierarchically porous heterostructures with high architectural diversity and elaborate functionality has become the focus of intensive research in recent years. − As a major family of porous materials, microporous zeolites are important solid catalysts for various reactions in the chemical industry. − However, some important catalytic reactions, such as biphasic interface reactions and tandem reactions, cannot be accomplished with zeolites as sole catalysts, due to the limited architectures and functionalities from single zeolite materials. In the case of biphasic interface catalysis, solid catalyst particles with anisotropic surface wettability are desirable to form thermodynamically stable Pickering emulsions. , In the latter case for tandem catalysis, bi/multifunctional solid catalysts with controllable architectures and spatial distributions of different catalytic components are needed for direct conversion of initial reactants into final products without separating or purifying the intermediates. − Therefore, delicate control of the anisotropic surface functionalization and spatial distribution of functional porous components on zeolites into hierarchically porous heterostructures in purposeful ways may offer new or improved catalytic properties in biphasic interface reactions or/and tandem reactions because of the anisotropic and synergistic effects.…”