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

The crystal structure of a bulk sample of the ferroelectric oxide SrBi2Ta2O9 refined using a combination of synchrotron and neutron powder diffraction data is reported. At room temperature SrBi2Ta2O9 has an orthorhombic structure with space group A21am. The bulk sample of SrBi2Ta2O9 studied was quenched from 600°C and was found to exhibit small, but significant amounts of disorder between the Sr and Bi cations.

Structural studies of cation disorder in the ferroelectric oxide SrBi2Ta2O9

Morphological changes of hydrophobic matrix and hydrophilic ionomers in water-swollen perfluorinated sulfonic acid membranes detected using small-angle X-ray scattering

Advanced nano-scale analyses such as x-ray absorption fine structure (XAFS), x-ray magnetic circular dichroism (XMCD) spectroscopy and x-ray fluorescence (XRF) with a ~100 nm spatial resolution have been routinely conducted by upgrading two x-ray beamlines BL37XU and BL39XU at SPring-8. The focusing beam size can be varied from 50 nm to 2 μm and high flux achieved at 1012 photons/s/0.01% b.w. with the beam size of 300 × 300 nm2 (full width at half maximum) at 12 keV.

Stable delivery of nano-beams for advanced nano-scale analyses

/pdf/charge-transfer-transition-in-two-dimensional-cs-co-3-1xphjalb49.pdf

Charge-transfer transition in two-dimensional Cs[Co(3-cyanopyridine)2][W(CN)8]·H2O as investigated by angle-resolved x-ray diffraction

The effects of thermal gradient on dynamical behavior of nanoparticles dispersed in polymer matrix were studied by X-ray photon correlation spectroscopy. Anisotropic motions of nanoparticles were observed when the sample was kept in a cell using a capillary tube covered with copper block. As the same experiment using another cell without such thermal gradient clearly demonstrated that even the small thermal gradient around the probe windows caused the anisotropic dynamical behavior.

/pdf/thermal-gradient-effect-on-the-dynamical-behavior-of-2tq72ljtoa.pdf

Masaki Takata

Papers

Structural studies of cation disorder in the ferroelectric oxide SrBi2Ta2O9

Morphological changes of hydrophobic matrix and hydrophilic ionomers in water-swollen perfluorinated sulfonic acid membranes detected using small-angle X-ray scattering

Stable delivery of nano-beams for advanced nano-scale analyses

Charge-transfer transition in two-dimensional Cs[Co(3-cyanopyridine)2][W(CN)8]·H2O as investigated by angle-resolved x-ray diffraction

Thermal gradient effect on the dynamical behavior of nanoparticles observed using X-ray photon correlation spectroscopy