Recent Advances in the Synthesis and Application of Two‐Dimensional Zeolites

Abstract

traditional hydrothermal syntheses would produce intermediate materials with 2D feature, such as MCM-22P, [ 7,8 ] PREFER, [ 9 ] which are composed of crystalline zeolite layers with the unit-cell thickness stacking on top of each other in ordered or disordered patterns. [10][11][12][13][14][15] Unlike traditional 3D zeolites, the crystal growth of frameworks in 2D layered zeolites is restricted in one particular direction, leaving lots of hydroxyl groups on layer surface. As zeolites are normally defi ned as 3D materials that possess regular micropore systems and consist of TO 4 tetrahedra, layered zeolite precursors containing silanols could not be regarded as zeolites in the strictest sense, but they are broadly included in the family of zeolite materials. Thus, the as-synthesized 2D zeolites are often denoted as layered zeolite precursors (the typical examples are shown in Table 1 ), [7][8][9] which would transform into their 3D order/disorder counterparts after removing organic molecules and condesation of interlayer silanols via calcination. [ 10 ] In the early research stage, the layered zeolite precursors are discovered accidentally in traditional hydrothermal syntheses, because we have limited control over the traditional synthesis process due to the incomplete understanding of crystallization mechanism. At that stage, one of the most attractive features of 2D zeolites is that they could transform into zeolite materials with hierarchical architectures. In some cases, the traditional synthesis produces hierarchical layered material, such as MCM-56, [ 26 ] in which the crystalline zeolite layers disorderly stacked. Furthermore, the recognition that the obtained layered precursors could be modifi ed into various hierarchical zeolite structures (such as delaminated, pillared, interlayer expanded and others) make them signifi cantly different from conventional 3D zeolite materials with rigid structures. Thus, the construction of hierarchical zeolite materials from the perspective of 2D layered zeolite precursors is an important research aspect during the past few years.With the improved synthetic techniques, layered zeolites are not only increasing in number, but also expanding the notion in composition and structure. One remarkable breakthrough in recent years is the discovery of 2D MFI nanosheets with the single unit-cell thickness (about 2 nm), which is achieved by adopting Gemini-type bifunctional surfactants as organic structure-directing agent (OSDA) in hydrothermal synthesis. [ 49 ] The calcined MFI nanosheets become a special kind of hierarchical zeolites Two-dimensional (2D) zeolites, originating from lamellar precursors, are a special kind of porous materials, in which crystalline zeolite nanolayers are weakly assembled in one particular direction. As there is no covalentbond between layers, the stacking sequences could be manipulated and possibly controlled to derive a family of zeolitic materials with structural diversity. The research on 2D zeolites arises from the primary casual discovery during ...

Two-Dimensional Zeolite Materials: Structural and Acidity Properties

“…In comparison to 3D zeolites, two-dimensional (2D) zeolites are an emerging type of nanoporous materials [6][7][8][9][10][11][12]. They are often made from the 2D layered precursors that contain stacked sheets of one-to-two unit cell or smaller thicknesses that are linked by weak van der Waals forces or hydrogen bonds.…”

“…Overviews of 2D zeolites in catalysis have been published by J.Čejka [6,9,43] and J. Sun [10] in the past few years.…”

Bridging the Gap between Structurally Distinct 2D Lamellar Zeolitic Precursors through a 3D Germanosilicate Intermediate

“…[1] Over the past decades,2 Dz eolites have demonstrated improved catalytic performance and potentially greater separation efficiencyc ompared to their 3D counterparts. [1] Over the past decades,2 Dz eolites have demonstrated improved catalytic performance and potentially greater separation efficiencyc ompared to their 3D counterparts.…”

“…Two-dimensional zeolites,w hich originate from lamellar precursors,h ave been an expanding subject of materials chemistry because of their flexible structures and desirable properties. [1] Over the past decades,2 Dz eolites have demonstrated improved catalytic performance and potentially greater separation efficiencyc ompared to their 3D counterparts. [2] Moreover,t he synthetic chemistry of 2D zeolites is very rich, as demonstrated by their use as basic building blocks to prepare zeolitic materials through intercalation, [3a] pillaring, [3b] delamination, [3c] interlayer-condensation, [3d] and organization-condensation processes.…”

Overview of Current and Future Perspectives of Saudi Arabian Natural Clinoptilolite Zeolite: A Case Review

“…An ion exchange method was proposed to modify local Saudi samples [75]. An additional article suggests further development of local zeolite resources to synthesize frameworks of zeolite (2D/3D) by approaching standard solvothermal methods [132] through connecting zeolite monolayers with various surfactant-templated nanosheets [133,134] considering also the demand that commercial applications will serve.…”