VESTA is a three-dimensional visualization system for crystallographic studies and electronic state calculations. It has been upgraded to the latest version, VESTA 3, implementing new features including drawing the external mor­phology of crystals; superimposing multiple structural models, volumetric data and crystal faces; calculation of electron and nuclear densities from structure parameters; calculation of Patterson functions from structure parameters or volumetric data; integration of electron and nuclear densities by Voronoi tessellation; visualization of isosurfaces with multiple levels; determination of the best plane for selected atoms; an extended bond-search algorithm to enable more sophisticated searches in complex molecules and cage-like structures; undo and redo in graphical user interface operations; and significant performance improvements in rendering isosurfaces and calculating slices.

VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data

Crystalline metal-organic frameworks (MOFs) are formed by reticular synthesis, which creates strong bonds between inorganic and organic units. Careful selection of MOF constituents can yield crystals of ultrahigh porosity and high thermal and chemical stability. These characteristics allow the interior of MOFs to be chemically altered for use in gas separation, gas storage, and catalysis, among other applications. The precision commonly exercised in their chemical modification and the ability to expand their metrics without changing the underlying topology have not been achieved with other solids. MOFs whose chemical composition and shape of building units can be multiply varied within a particular structure already exist and may lead to materials that offer a synergistic combination of properties.

The Chemistry and Applications of Metal-Organic Frameworks

J. Appl. Cryst.の発刊に際して

Adsorptive separation is very important in industry. Generally, the process uses porous solid materials such as zeolites, activated carbons, or silica gels as adsorbents. With an ever increasing need for a more efficient, energy-saving, and environmentally benign procedure for gas separation, adsorbents with tailored structures and tunable surface properties must be found. Metal–organic frameworks (MOFs), constructed by metal-containing nodes connected by organic bridges, are such a new type of porous materials. They are promising candidates as adsorbents for gas separations due to their large surface areas, adjustable pore sizes and controllable properties, as well as acceptable thermal stability. This critical review starts with a brief introduction to gas separation and purification based on selective adsorption, followed by a review of gas selective adsorption in rigid and flexible MOFs. Based on possible mechanisms, selective adsorptions observed in MOFs are classified, and primary relationships between adsorption properties and framework features are analyzed. As a specific example of tailor-made MOFs, mesh-adjustable molecular sieves are emphasized and the underlying working mechanism elucidated. In addition to the experimental aspect, theoretical investigations from adsorption equilibrium to diffusion dynamics via molecular simulations are also briefly reviewed. Furthermore, gas separations in MOFs, including the molecular sieving effect, kinetic separation, the quantum sieving effect for H2/D2 separation, and MOF-based membranes are also summarized (227 references).

Selective gas adsorption and separation in metal–organic frameworks

Metal–Organic Frameworks for Separations

We have developed a new attachment for thin film x‐ray measurements equipped with the large Debye‐Scherrer camera at BL02B2 of the SPring‐8. It is quite easy to handle and control the attachment using user‐friendly computer programs. It is also notable that the attachment realizes both low‐glancing‐angle incident beam condition and in‐plane measurement condition. The attachment enables us to measure high precision x‐ray diffraction data from many kinds of thin films with the Debye‐Scherrer camera. Using this attachment we try to analyze some dimensionally controlled thin film structures.

A New Attachment of the Large Debye-Scherrer Camera at BL02B2 of the SPring-8 for Thin Film X-ray Diffraction

Higher-order Structure Analysis of Polyethylene Thin Films by In-situ Synchrotron Grazing-incdence Small-angle and Wide-angle X-ray Scattering Measurements

We report the first in situ NMR observation of 2H2 adsorbed inside [Cu3(btc)2] (HKUST-1; btc: benzenetricarboxylate) at ambient temperature and pressure. Hydrogen adsorption behavior was investigat...

First In Situ NMR Observation of Hydrogen Adsorbed inside [Cu3(btc)2] at Ambient Temperature and Pressure

Hierarchical structural features of Vinylidene fluoride-trifluoroethylene (VDF-TrFE) copolymers during the phase transition have been successfully investigated in detail by in-situ simultaneous measurements of DSC and SAXS/WAXD utilizing synchrotron radiation. In a heating process at a constant rate of 1 °C/min, a broad endothermic peak was measured for a VDF-TrFE copolymer from ca. 75°C to ca. 135°C. On the other hand, WAXD data indicated that the phase transition from the crystal form II to the high-temperature (HT) phase began to occur at ca. 105°C. With an increase in temperature from ca. 75° C to ca. 105° C (temperature region A), lamellar staking distance (long period) and lamellar thickness evaluated in SAXS data analyses slightly increased though the crystallite size (the lateral dimension of the lamellae) was almost constant. The (110) reflections of the crystal form II gradually decreased in integrated intensity and scattering from the amorphous region increased instead, which implied that lamellae in crystal form II became partially disordered before the phase transition.

https://iopscience.iop.org/article/10.1088/1742-6596/184/1/012014/pdf

Correlated changes in meso- and nano-scale hierarchical structure of Vinylidene fluoride-trifluoroethylene random copolymers investigated by simultaneous measurements of DSC and SAXS/WAXD utilizing synchrotron radiation

The structural phase transformations in the chalcopyrite semiconductor AgInTe2 have been studied up to 10 GPa on both pressure increase and decrease. The experiment were carried out using angle-dispersive X-ray diffraction with synchrotron radiation and an image plate. The diffraction patterns of AgInTe2 at ambient pressure reveal two coexisting phases: the first has the chalcopyrite structure while the second has a zinc blende like structure. On pressure increase both phases transformed at 3-4 GPa to a cationdisordered structure with spacegroup Cmcm, the atomic coordinates of which v=0.75 for Ag or In and v=0.25 for Te correspond to an NaCl-like structure. On pressure increase the Cmcm phase was stable up to at least 10.25 GPa. On pressure decrease, the chalcopyrite phase started to reappear at 0.55 GPa, and the Cmcm phase disappeared completely at ambient pressure. In addition to the experimental study, we have also performed density functional theory calculations. The calculated transition pressure from the chalcopyrite phase to the Cmcm phase is 4.08 GPa, and the calculated atomic positions in the Cmcm phase are in excellent agreement with those determined experimentally.

/pdf/high-pressure-and-low-temperature-charge-density-study-of-40vdpf4viy.pdf

Masaki Takata

Papers

A New Attachment of the Large Debye-Scherrer Camera at BL02B2 of the SPring-8 for Thin Film X-ray Diffraction

Higher-order Structure Analysis of Polyethylene Thin Films by In-situ Synchrotron Grazing-incdence Small-angle and Wide-angle X-ray Scattering Measurements

First In Situ NMR Observation of Hydrogen Adsorbed inside [Cu3(btc)2] at Ambient Temperature and Pressure

Correlated changes in meso- and nano-scale hierarchical structure of Vinylidene fluoride-trifluoroethylene random copolymers investigated by simultaneous measurements of DSC and SAXS/WAXD utilizing synchrotron radiation

High-pressure and low-temperature charge-density study of Pr1−xCaxCoO3 by SR powder diffraction