Intergrowth Zeolites, Synthesis, Characterization, and Catalysis

Abstract

Microporous zeolites that can act as heterogeneous catalysts have continued to attract a great deal of academic and industrial interest, but current progress in their synthesis and application is restricted to single-phase zeolites, severely underestimating the potential of intergrowth frameworks. Compared with single-phase zeolites, intergrowth zeolites possess unique properties, such as different diffusion pathways and molecular confinement, or special crystalline pore environments for binding metal active sites. This review first focuses on the structural features and synthetic details of all the intergrowth zeolites, especially providing some insightful discussion of several potential frameworks. Subsequently, characterization methods for intergrowth zeolites are introduced, and highlighting fundamental features of these crystals. Then, the applications of intergrowth zeolites in several of the most active areas of catalysis are presented, including selective catalytic reduction of NOx by ammonia (NH 3 -SCR), methanol to olefins (MTO), petrochemicals and refining, fine chemicals production, and biomass conversion on Beta, and the relationship between structure and catalytic activity was profiled from the perspective of intergrowth grain boundary structure. Finally, the synthesis, characterization, and catalysis of intergrowth zeolites are summarized in a comprehensive discussion, and a brief outlook on the current challenges and future directions of intergrowth zeolites is indicated.

The Current Understanding of Mechanistic Pathways in Zeolite Crystallization

“…The third type involves intergrowths (Figure c), which typically require a high degree of similarity between the two zeolite structures. The benefits of intergrown zeolites include enhanced particle morphologies (e.g., self-pillared and other hierarchical architectures , ) and the possibility of combining two different framework structures into a product with unique properties, such as MEL/MFI, CHA/AEI, , FAU/EMT, or RTH/ITE intergrowths. In many cases, this type of IZT requires the use of specific OSDAs, which was highlighted in a collaborative study by Gómez-Bombarelli, Corma, Moliner, and Román that established a database to facilitate OSDA selection for intergrowth design .…”

Pore Restructuring of Peptide Frameworks by Mutations at Distal Packing Residues

“…These materials find widespread utility and are continuously evolving to meet greater challenges in industrial and sustainable applications, serving as catalysts, adsorbents, and molecular sieves. Among the most prominent examples of this category are zeolites, , metal–organic frameworks (MOFs), − and covalent organic frameworks (COFs). − The dimensions, shapes, and functional groups within their pores determine the specific chemical processes that can occur within the material. In this context, the pores within frameworks have structural and functional analogy to the active sites found in proteins, − which also contain precisely sized, functionalized pockets for binding or catalysis.…”

Coupling Different Periodic Building Units for Intergrowth Zeolites

“…While crystallographically ordered zeolites are a class of crystalline microporous materials with regularity in pore size and shape, phase competition in their polymorphs can lead to remarkable changes in many important properties of the resulting intergrowth products compared to completely ordered zeolite phases, notably in molecular diffusion pathway and confinement and access to catalytically active sites, both acidic and metallic. − Thus, the systematic control of zeolite phase competition in the synthesis of intergrowth zeolites is of both fundamental and practical importance, being of direct relevance to “designer zeolites” with desired properties for more sustainable catalysis, like in the case of new ordered zeolite structures. Recently, computational simulations and data mining have enabled finding of thermodynamically favorable biselective organic structure-directing agents (SDAs) leading to both known and hypothesized intergrowths. − However, little attention has been paid to how or even whether the extent of this competition is systematically controlled by modifying the type and concentration of inorganic components in the synthesis mixture. , Furthermore, less attention has been devoted to the prediction and synthesis of novel intergrowth zeolites …”