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ZIF-67 is a representative type of metal–organic framework (MOF) developed for the oxygen reduction reaction (ORR) owing to its robust structure in alkaline electrolytes and the presence of the redox-active Co2+ species in the structure. In this work, the improvement of the ORR electrolytic performance of ZIF-67 in its pure phase by optimization of its crystal morphology and crystal facets has been presented. ZIF-67 nanocubes exhibit higher ORR activity than their bulk crystals. The enriched (100) facet in the nanocube crystals provides a higher number of exposed Co2+ sites resulting in improved ORR performances. Moreover, DFT study suggests a distinguished mechanism in the (100) facet highlighting the importance of crystal facets in electrochemical performances. [ABSTRACT FROM AUTHOR]

Zeolitic imidazolate framework-8 (ZIF-8) with different sizes and morphologies were successfully synthesized using a membrane dispersion reactor (MDR). The MDR synthesis applied in this paper was expected to be an efficient and economical way to synthesize ZIF materials. [ABSTRACT FROM AUTHOR]

Two organic-polyoxometalates (organic-POMs) hybrids were constructed by fan-shaped 1-methyl-3-[3, 4, 5-tris(octadecyloxy) benzyl]imidazolium salts (labelled as I–Cl) and triethyl-[3, 4, 5-tris (octadecyloxy) benzyl] ammonium salts (labelled as Q–Cl) and Keggin anions [SiW12O40]4−by electrostatic interaction. Self-assembled behaviours of two aggregates in organic solvent and solid state were investigated in detail by scanning electron microscopy, transmission electron microscopy and X-ray analysis. The mixed solution of chloroform–methanol or chloroform–acetone provided the stable environment for aggregates and aggregates showed a uniform micron size. X-ray analysis results showed that flower-like aggregates morphology of I4[SiW12O40] based on imidazole ring as ‘head’ in organic cations was formed by the stacking of multilamellar discs and kept the lamellar structure in solid state. Bulk thorn spheres appeared in Q4[SiW12O40] aggregates, which were formed by closely interspersed of lots flatted blocks with hexagonal structure characteristics in solid state. The comprehension for the self-assembly morphology and solid structure of organic-polyoxometalate hybrids would help us to use easily modified organic moiety and functional inorganic polyoxoanions as blocks to build novel and giant supramolecular architecture. [ABSTRACT FROM AUTHOR]

In this work, we fabricate new yolk–shell Pd@ZIF-8 (ZIF = zeolitic imidazolate framework) nanoparticles (NPs) through reactions of the preformed core–shell Pd@ZnO NPs with 2-methylimidazole under mild conditions. In this method, ZnO is used as the self-template and the Zn2+ source for the formation of the ZIF-8 shell. The morphology, composition and structure of the as-prepared yolk–shell nanomaterial are characterized by scanning electron microscopy, transmission electron microscopy, high resolution transmission electron microscopy, powder X-ray diffraction, energy dispersive X-ray spectroscopy, and inductively coupled plasma atomic emission spectroscopy. The formation of this well-defined yolk–shell nanostructure is highly dependent on the solvent system and reaction time. This nanomaterial can be employed as an excellent heterogeneous catalyst for the liquid-phase hydrogenation of olefins with high size-selectivity at room temperature, which is mainly due to the inherent porous structure of the outer ZIF-8 shell along with the enclosed Pd NPs. The nanocatalyst system can be recycled at least three times without any evident loss of the catalytic efficiency. [ABSTRACT FROM AUTHOR]