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

Structural studies of endohedral metallofullerenes using synchrotron radiation powder profiles were described with two examples. A two-dimensional (2D) arrangement of metallofullerenes for both M@C82 (M = Y, La, Ce, Pr) and (M2Cy)@C82 (M = Er, y = 0, 2; M = Sc, y =2) is crystallized with 1:2 fullerene/toluene molecular ratio. The difference of the molecular arrangements strongly correlates with an orientation of metallofullerenes in the 2D layer. Systematically structural studies have been carried out for 24 different kinds of endohedral metallofullerenes, MxC2n (M = La, Y, Sc, Lu, Ti, Eu, Er, Hf, Sc3N; 34 ≤ n ≤ 43), as 1:1 co-crystals with solvent toluene molecules. It is found that the volume for one fullerene and one toluene molecule linearly depends on the number of carbon atoms in the fullerene cage. This linear dependence provides a metallofullerene diagnostics diagram that has universal importance for structural characterization of the cluster endohedral fullerenes.

Smart Crystallography in Materials Science at SPring-8: In the case of Endohedral Metallofullerene

Since 2002, the structural science via Maximum Entropy Method based on synchrotron radiation(SR) diffraction data has driven an innovation of structural chemistry in Coordination Chemistry at SPring-8. The first successful contribution of the MEM Structural Science was a discovery of the peculiar structure of absorbed gas molecules in the nanopore of coordination polymer. The revealed one-dimensional array structure of absorbed gas molecules with no charge transfer made chemists recognize the power of Synchrotron Radiation as a probe of electrons in materials. The development of the MEM/Rietveld Method is described in terms of absorbed molecular site prediction as well as finding charge transfer among host-guest molecules. The expected role of the Next Generation Synchrotron Radiation facility under construction at Tohoku University Campus is also noted. 

Innovation in Coordination Structural Chemistry by Synchrotron Radiation Science and Maximum Entropy Method

MEMによるターゲット構造可視化法の開発：タンパク質を封じ込めた人工カプセルの合成と構造決定;MEMによるターゲット構造可視化法の開発：タンパク質を封じ込めた人工カプセルの合成と構造決定;Development of a MEM Structure Visualization Method: Synthesis and Structural Analysis of Artificial Capsule Enclosing Protein

Making a seismic solar model and an estimate of the neutrino fluxes

The composite crystal, Nd13Fe46B41, was examined utilizing synchrotron radiation. Diffraction profiles along the c* axis were measured at the wavelength of Nd and Fe absorption edges. It was clarified that two subsystems, Nd and Fe subsystems, contribute differently, and that the modulation periods of Nd and Fe are slightly different. The widths of peaks from Nd and Fe reveal that the fundamental period of the Nd subsystem fluctuates much more than that of the Fe subsystem.

Masaki Takata

Papers

Smart Crystallography in Materials Science at SPring-8: In the case of Endohedral Metallofullerene

Innovation in Coordination Structural Chemistry by Synchrotron Radiation Science and Maximum Entropy Method

Making a seismic solar model and an estimate of the neutrino fluxes

Separation of Two Subsystems in Nd 13 Fe 46 B 41 Composite Crystal Utilizing Synchrotron Radiation