Basic concepts of computer topological analysis of crystal structures realized in the current version of the program package ToposPro are considered. Applications of the ToposPro methods to various classes of chemical compounds—coordination polymers, molecular crystals, supramolecular ensembles, inorganic ionic compounds, intermetallics, fast-ion conductors, microporous materials—are illustrated by many examples. It is shown that chemically and crystallographically different structures can be automatically treated in a similar way with the ToposPro approaches.

http://pubs.acs.org/doi/pdf/10.1021/cg500498k

Applied Topological Analysis of Crystal Structures with the Program Package ToposPro

Recent advances in transition metal catalyzed oxidation of organic substrates with molecular oxygen.

Linkers and/or Multiple Building Units and the Minimal Transitivity Principle Mian Li,† Dan Li,† Michael O’Keeffe,*,‡,§ and Omar M. Yaghi †Department of Chemistry, Shantou University, Guangdong 515063, P. R. China ‡Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287, United States Graduate School of EEWS (WCU), KAIST, 373-1, Guseng Dong, Yuseong Gu, Daejeon 305-701, Republic of Korea Department of Chemistry, University of CaliforniaBerkeley and Lawrence Berkeley National Laboratory, Berkeley, California 94720-1460, United States

/pdf/topological-analysis-of-metal-organic-frameworks-with-3mci8vr8d9.pdf

Topological Analysis of Metal–Organic Frameworks with Polytopic Linkers and/or Multiple Building Units and the Minimal Transitivity Principle

Oxidative dehydrogenation of ethane and propane : How far from commercial implementation?

This paper summarizes the main data appeared in the last years on the oxidative dehydrogenation (ODH) of short chain alkanes on supported vanadium oxide catalysts. The acid-base character of metal oxide support influences the dispersion of vanadium on the surface of the support, as well as the nature of the vanadium species. The reducibility and structure of surface vanadium oxide species and the acid-base character of catalysts, in addition to their catalytic properties in the ODH of C2–C4 alkanes, strongly depend on the metal oxide used as support and the vanadium loading. In this way, it appears that tetrahedral V5+-species are active and selective sites in the ODH of C2–C4 alkanes. The effect of the coordination number and aggregation state of surface vanadium oxide species, and the presence of acid/base sites on the catalytic behavior of supported vanadium oxide catalysts are discussed. It is concluded that these are important factors that must be considered to develop selective catalysts in ODH reactions.

Oxidative dyhydrogenation of short chain alkanes on supported vanadium oxide catalysts

Gallium-modified ZSM5 zeolites, containing 2, 3, and 4 wt % Ga, were prepared by incipient wetness impregnation with gallium(III) nitrate solutions of HZSM5 samples with SAR values of 24 and 35. The modified zeolites were subjected to two consecutive treatment cycles of reduction in hydrogen and reoxidation in air. The catalysts were characterized by nitrogen physical adsorption, 29Si and 27Al MAS NMR, temperature-programmed reduction, temperature-programmed desorption of ammonia, X-ray absorption spectroscopy, and infrared spectroscopy in the OH stretching region and in the region of skeletal vibrations of adsorbed pyridine. Catalytic activity and selectivity were measured in propane conversion reactions at 703 K. Results were rationalized in terms of correlations among the framework Ga/Al ratio, density, strength and type of acidity, gallium cluster sizes, reducibility of gallium, and propane aromatization activity. It was found that the dispersion of the gallium species was a function only of the frame...

Correlations between Dispersion, Acidity, Reducibility, and Propane Aromatization Activity of Gallium Species Supported on HZSM5 Zeolites

Pt-TiO{sub 2}-{gamma} Al{sub 2}O{sub 3} catalyst. 1: Dispersion of platinum on alumina-grafted titanium oxide

Polycrystalline solid solutions of phosphate and vanadate calcium apatites were synthesized and studied by XRD, XPS, 31P and 51V NMR, FTIR and UV spectroscopies. Homogeneous distributions of vanadium within the solid and the surface were obtained. While 51V NMR spectra suggest an axial symmetry of the vanadate
 group, FTIR spectra indicate distortion from essentially C3v symmetry in solid solutions with low vanadium content to Cs for pure vanadate apatite, in agreement with the site symmetry group of phosphate in hydroxyapatite. Refinements of XRD pattern of vanadate apatite by Rietveld method confirm the Cs
 point
 group attribution. Three vanadium oxygen bond lengths were found around 168 pm and one close to 174 pm,
 suggesting that the Cs
 point group could be generated by a small distortion from C3v symmetry. Analysis of UV spectra confirms that distortion from Td symmetry increases with vanadium
 content and suggests
 some contraction of the vanadate ion in the apatite lattice.

Structure of vanadate in calcium phosphate and vanadate apatite solid solutions

Vanadium Phosphorus Oxide Catalyst Modified by Niobium Doping for Mild Oxidation of n-Butane to Maleic Anhydride

Crystal-structure topologies, represented by periodic nets, are described by labelled quotient graphs (or voltage graphs). Because the edge space of a finite graph is the direct sum of its cycle and co-cycle spaces, a Euclidian representation of the derived periodic net is provided by mapping a basis of the cycle and co-cycle spaces to a set of real vectors. The mapping is consistent if every cycle of the basis is mapped on its own net voltage. The sum of all outgoing edges at every vertex may be chosen as a generating set of the co-cycle space. The embedding maps the cycle space onto the lattice L. By analogy, the concept of the co-lattice L* is defined as the image of the generators of the co-cycle space; a co-lattice vector is proportional to the distance vector between an atom and the centre of gravity of its neighbours. The pair (L, L*) forms a complete geometric descriptor of the embedding, generalizing the concept of barycentric embedding. An algebraic expression permits the direct calculation of fractional coordinates. Non-zero co-lattice vectors allow nets with collisions, displacive transitions etc. to be dealt with. The method applies to nets of any periodicity and dimension, be they crystallographic nets or not. Examples are analyzed: α-cristobalite, the seven unstable 3-periodic minimal nets etc.

Jean-Guillaume Eon

Papers

Correlations between Dispersion, Acidity, Reducibility, and Propane Aromatization Activity of Gallium Species Supported on HZSM5 Zeolites

Pt-TiO{sub 2}-{gamma} Al{sub 2}O{sub 3} catalyst. 1: Dispersion of platinum on alumina-grafted titanium oxide

Structure of vanadate in calcium phosphate and vanadate apatite solid solutions

Vanadium Phosphorus Oxide Catalyst Modified by Niobium Doping for Mild Oxidation of n-Butane to Maleic Anhydride

Euclidian embeddings of periodic nets: definition of a topologically induced complete set of geometric descriptors for crystal structures.