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  1. Abstract

    Two‐dimensional MFI zeolite nanosheets contain Brønsted acid sites partially confined at the intercept between micro‐ and mesopores. These acid sites exhibit exceptional reactivities and stabilities for C=C bond coupling and ring‐closure reactions that transform light aldehydes to aromatics. These sites are much more effective than those confined within the micropores of MFI crystallites and those unconfined on H4SiW12O40clusters or mesoporous aluminosilicate Al‐MCM‐41. The partially confined site environment solvates and stabilizes the transition states of the kinetically relevant steps during aromatization.

     
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  4. Zeolites are generally defined as three-dimensional (3D) crystalline microporous aluminosilicates in which silicon (Si4+) and aluminum (Al3+) are coordinated tetrahedrally with oxygen to form large negative lattices and consequent Brønsted acidity. Two-dimensional (2D) zeolite nanosheets with single-unit-cell or near single-unit-cell thickness (~2–3 nm) represent an emerging type of zeolite material. The extremely thin slices of crystals in 2D zeolites produce high external surface areas (up to 50% of total surface area compared to ~2% in micron-sized 3D zeolite) and expose most of their active sites on external surfaces, enabling beneficial effects for the adsorption and reaction performance for processing bulky molecules. This review summarizes the structural properties of 2D layered precursors and 2D zeolite derivatives, as well as the acidity properties of 2D zeolite derivative structures, especially in connection to their 3D conventional zeolite analogues’ structural and compositional properties. The timeline of the synthesis and recognition of 2D zeolites, as well as the structure and composition properties of each 2D zeolite, are discussed initially. The qualitative and quantitative measurements on the acid site type, strength, and accessibility of 2D zeolites are then presented. Future research and development directions to advance understanding of 2D zeolite materials are also discussed. 
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