The rotational motion of polyanions in solid-state materials is known as relating to the onset of an order-disorder phase transition with several orders of magnitude enhancement in ion conductivity. A major drawback in this class of materials is their high phase transition temperatures and thereby poor conductivities at room temperature. Here, I introduce a novel mechanism to drastically reduce the phase transition temperature by exploiting pseudorotation of hydride complexes with high hydrogen coordination. I demonstrate this mechanism for an existing material Li5MoH11 containing MoH93－, and present a strong potential of this material to exhibit an unprecedentedly high room-temperature lithium ion conductivity.
What mechanical properties can be expected for materials composed of interlocked backbones has been a long-standing issue in materials science since the first reports on polycatenane and polyrotaxane in the 1970s. We successfully synthesized a three-dimensional porous metal-organic crystal composed of a ［2］ catenane. This porous crystal dynamically changes its geometry upon guest molecule release, uptake and exchange, and also upon temperature variation even in a low temperature range. We indented the crystal and obtained the Young’s moduli of 1.8 GPa in N,N-dimethylformamide, which is the lowest among those reported so far for porous metal-organic crystals.
Zeolite is a microporous crystalline material which is widely used as industrial application such as catalyst and adsorbent, but its crystallization mechanism is still unclear. Authors have conducted studies to clarify the crystallization mechanism of zeolites by observing the transformation process of amorphous precursors into zeolite under various synthetic conditions by using pair distribution function analysis combined with other analytical techniques. This article introduces some of these studies.
The importance of the caffeine removal technique from water has been increased since it reduces the risk of diseases such as sleep disorders and allergic reactions. A layered expandable clay mineral smectite can adsorb the caffeine molecules in the interlayer and surface. The adsorption capacity increases with exchanging the interlayer monovalent sodium ions for trivalent aluminum ions. The mechanism is revealed from the X-ray diffraction and molecular dynamics simulations. The interlayer distance and area are large enough for caffeine molecules to intercalate in the aluminum-substituted smectite. On the other hand, the original smectite delaminates in water due to the weak interaction between interlayer sodium ions and the smectite surface resulting in low adsorption of caffeine molecules.
Functions of porous crystalline materials are basically governed by molecular recognition in their pores. We have developed novel porous crystals, metal-macrocycle frameworks（MMFs）, having one-dimensional nano-channels equipped with multiple asymmetric binding pockets. Single-crystal X-ray diffraction analyses revealed that several guest molecules including peptides and terpenes were site-selectively arranged in the pore through multipoint interactions with hydrophobic and hydrophilic functionalities asymmetrically placed on the pore surfaces. The unique recognition ability was also applied to the development of specific catalytic reactions based on the confined effect.