Highly selective conversion of methanol to propylene: design of an MFI zeolite with selective blockage of (010) surfaces

The Development of iDPC-STEM and Its Application in Electron Beam Sensitive Materials

The main aspects of material research: material synthesis, material structure, and material properties, are interrelated. Acquiring atomic structure information of electron beam sensitive materials by electron microscope, such as porous zeolites, organic-inorganic hybrid perovskites, metal-organic frameworks, is an important and challenging task. The difficulties in characterization of the structures will inevitably limit the optimization of their synthesis methods and further improve their performance. The emergence of integrated differential phase contrast scanning transmission electron microscopy (iDPC-STEM), a STEM characterization technique capable of obtaining images with high signal-to-noise ratio under lower doses, has made great breakthroughs in the atomic structure characterization of these materials. This article reviews the developments and applications of iDPC-STEM in electron beam sensitive materials, and provides an outlook on its capabilities and development.

Improvement of adsorption and catalytic properties of zeolites by precisely controlling their particle morphology

An aluminosilicate zeolite has a porous structure with openings comparable to the molecular size, which endows it with unique adsorptive and catalytic properties that are highly dependent on its chemical composition and crystal morphology. Thus, the precise control or rational design of zeolite's particle morphology has attracted much attention as it can greatly improve the adsorptive separation and catalytic properties by effectively adjusting the diffusion path of adsorbates, reactants and products. This paper reviews the recent progress made in the synthesis and application of zeolites with a specific crystal/particle morphology with emphasis on the control of the crystal size and facet exposure degree, oriented assembly of crystals, creation of hierarchical porous structures and synthesis of core-shell structures. It is shown that an appropriate decrease of the crystal size and/or an increase of the exposure degree of certain facets by adding seeds and optimizing the synthesis conditions enhances the catalytic stability and product selectivity in some reactions. This can also be achieved by introducing plenty of mesopores and/or macropores in zeolites as a result of significant alleviation of diffusion limitation. Assembly of zeolite crystals into membranes on porous substrates improves the adsorptive separation performance of zeolites, for e.g. alcohol/water mixture and xylene and butane isomers. Core-shell-structured composites with metal nanoparticles or subnanoparticles as the core and the zeolite, including its modified counterpart, as the shell show excellent catalytic performance in some hydrogenation, dehydrogenation and oxidation reactions. In addition, attempts to illustrate the relationship between zeolite's particle morphology and its catalytic performance are discussed and strategies for the rational design of zeolite's particle size and behavior are envisioned.

Direct synthesis of [B,H]ZSM-5 by a solid-phase method: AlF siting and catalytic performance in the MTP reaction

[B,H]ZSM-5 directly synthesized by a solid-phase method with tuned Al_F siting and acidity exhibited a longer lifetime in the MTP reaction.