Construction of Hierarchical Films via Layer-by-Layer Assembly of Exfoliated Unilamellar Zeolite Nanosheets.

Zeolites have been widely applied as versatile catalysts, sorbents, and ion exchangers with unique porous structures showing molecular sieving capability. In these years, it is reported that some layered zeolites can be delaminated into molecularly thin 2-dimensional (2D) nanosheets characterized by inherent porous structures and highly exposed active sites. In the present study, two types of zeolite nanosheets with distinct porous structures with MWW topology (denoted mww) and ferrierite-related structure (denoted bifer) are deposited on a substrate through the solution process via electrostatic self-assembly.

Exfoliated Ferrierite-Related Unilamellar Nanosheets in Solution and Their Use for Preparation of Mixed Zeolite Hierarchical Structures.

Direct exfoliation of layered zeolites into solutions of monolayers has remained unresolved since the 1990s. Recently, zeolite MCM-56 with the MWW topology (layers denoted mww) has been exfoliated directly in high yield by soft-chemical treatment with tetrabutylammonium hydroxide (TBAOH). This has enabled preparation of zeolite-based hierarchical materials and intimate composites with other active species that are unimaginable via the conventional solid-state routes.

Liquid dispersions of zeolite monolayers with high catalytic activity prepared by soft-chemical exfoliation.

The most effective approach to practical exploitation of the layered solids that often have unique valuable properties-such as graphene, clays, and other compounds-is by dispersion into colloidal suspensions of monolayers, called liquid exfoliation. This fundamentally expected behavior can be used to deposit monolayers on supports or to reassemble into hierarchical materials to produce, by design, catalysts, nanodevices, films, drug delivery systems, and other products. Zeolites have been known as extraordinary catalysts and sorbents with three-dimensional structures but emerged as an unexpected new class of layered solids contributing previously unknown valuable features: catalytically active layers with pores inside or across.

Pillaring of layered zeolite precursors with ferrierite topology leading to unusual molecular sieves on the micro/mesoporous border.

Layered zeolite materials with FER layer topology can produce various condensed and expanded structures including zeolite frameworks, FER and CDO, their interlayer expanded forms (IEZ), and organic-intercalated and pillared derivatives. This work concerns pillaring of the surfactant-swollen derivative with a gallery height of ca. 2.

Characterization of Co and Fe-MCM-56 catalysts for NH-SCR and NO decomposition: An in situ FTIR study.

Two-step preparation of iron and cobalt-containing MCM-56 zeolites has been undertaken to evaluate the influence of their physicochemical properties in the selective catalytic reduction (NH-SCR or DeNOx) of NO using NH as a reductant. Zeolites were prepared by the selective leaching of the framework cations by concentrated HNO solution and NHF/HF mixture and consecutively, introduction of Co and Fe heteroatoms, in quantities below 1wt%. Further calcination allowed to obtain highly dispersed active species.