[en] This review deals with key methods of synthesis and characterization of metal-organic frameworks (MOFs). The modular structure affords a wide variety of MOFs with different active metal sites and organic linkers. These compounds represent a new stage of development of porous materials in which the pore size and the active site structure can be modified within wide limits. The set of experimental methods considered in this review is sufficient for studying the short-range and long-range order of the MOF crystal structure, determining the morphology of samples and elucidating the processes that occur at the active metal site in the course of chemical reactions. The interest in metal-organic frameworks results, first of all, from their numerous possible applications, ranging from gas separation and storage to chemical reactions within the pores. The bibliography includes 362 references

[en] Tribological materials from the wheel and the wheel chock of a railway train were studied. The samples were taken from new and used wheels and wheel chock. Experimental x-ray absorption near edge spectra (XANES) spectra above the Fe L2,3 edges show the variations in the shape of the Fe L 2,3 edge fine structure, that correspond to the formation of Fe oxidized layer during the process of dry friction. Elemental analysis shows the large variations of element's distribution along the surface within 10 nm depth of damaged sample.

[en] The data on the dynamics of structural changes in the composite cathode material based on iron(III) fluoride studied by the operando synchrotron X-ray spectroscopy and diffraction combined with the density functional theory (DFT) are reported. Based on the FeF₃ structure determined by X-ray crystallography the crystal structure of Li_xFeF₃ for 0 < x < 0.5 is modeled by the geometry optimization. The crystal structure models for 0.5 < x < 1 are predicted using the evolutionary algorithms. The Fe K-edge X-ray absorption spectra are calculated for these models and compared with the experimental data.

[en] The development of the next generation synchrotron radiation sources - free electron lasers - is approaching to become an effective tool for the time-resolved experiments aimed to solve actual problems in various fields such as chemistry’ biology’ medicine’ etc. In order to demonstrate’ how these experiments may be performed for the real systems to obtain information at the atomic and macromolecular levels’ we have performed a molecular dynamics computer simulation combined with quantum chemistry calculations for the human phosphoglycerate kinase enzyme with Mg containing substrate. The simulated structures were used to calculate coherent X-ray diffraction patterns’ reflecting the conformational state of the enzyme, and Mg K-edge X-ray absorption spectra, which depend on the local structure of the substrate. These two techniques give complementary information making such an approach highly effective for time-resolved investigation of various biological complexes, such as metalloproteins or enzymes with metal-containing substrate, to obtain information about both metal-containing active site or substrate and the atomic structure of each conformation. (paper)

[en] A peculiar property of ceria is the ease to form oxygen vacancies, producing reactive sites or facilitating ionic diffusion. For these reasons ceria promotes catalytic activities for a number of important reactions when it is used as a support for transition metals. In our work we study the temporal evolution of oxygen vacancies formation by time-resolved XANES at Ce K- edge and XRD measurements on CeO₂/Pt nanoparticles, successfully monitoring the reaction of CO oxidation. (paper)

[en] Ce L1-edge high-energy-resolution fluorescence detected (HERFD) X-ray absorption spectroscopy (XAS) was applied to unravel the electronic structure of Pt-promoted CeO₂ nanoparticles under different redox conditions. The Ce Lγ₃ emission line was chosen for partial fluorescence yield detection to improve the XAS spectral resolution. Oxygen vacancies were formed on the surface of ceria nanoparticles upon reducing in 5% CO in He. Theoretical Ce L₁-edge simulations showed good agreement with the experimental data.

[en] AlN ferromagnetic nanorods with 5 at.% of copper were studied by using x-ray absorption spectroscopy (XAFS) above the Cu K- and L3- edges. Theoretical simulations of XAFS spectra clearly identify a formation of small copper clusters inside AlN lattice. Average size of clusters was estimated to be 50-70 atoms from the analysis of both XANES (X-ray Absorption Near Edge Spectroscopy) and EXAFS (Extended X-ray Absorption Fine Structure) regions of spectra. Calculations of magnetic moments for different types of point copper defects in AlN lattice were made.

[en] Fe-doped AlN nanorods were studied by means of x-ray absorption spectroscopy above the Fe K- and L_2,3- edges. Theoretical simulations of the x-ray absorption spectra show that Fe atoms mainly substitute Al. A minor fraction of Fe interstitials or Fe-Al-N ternary alloy can be identified as well. Bader's AIM analysis predicts that neutral substitutional FeAl defect is in 2⁺ charge state, though Al in pure AlN is in 3⁺ charge state. Fe L_2,3 absorption spectra and photoluminescence data indicate the coexistence of Fe²⁺/Fe³⁺ in AlN:Fe nanorods so different charge states of substitutional Fe_Al should co-exist.

[en] Finite difference method (FDM) implemented in the FDMNES software [Phys. Rev. B, 2001, 63, 125120] was revised. Thorough analysis shows, that the calculated diagonal in the FDM matrix consists of about 96% zero elements. Thus a sparse solver would be more suitable for the problem instead of traditional Gaussian elimination for the diagonal neighbourhood. We have tried several iterative sparse solvers and the direct one MUMPS solver with METIS ordering turned out to be the best. Compared to the Gaussian solver present method is up to 40 times faster and allows XANES simulations for complex systems already on personal computers. We show applicability of the software for metal-organic [Fe(bpy)₃]²⁺ complex both for low spin and high spin states populated after laser excitation. (paper)

[en] In the current work we present a detailed analysis of the hydride phase formation in industrial Pd/C nanocatalysts by means of combined in situ X-ray absorption spectroscopy (EXAFS), X-ray diffraction (XRD) and volumetric measurements for the temperatures from - 10 to 50 °C in the hydrogen pressure range from 0 to 1000 mbar. α- and β- hydride phases are clearly distinguished in XRD. For the first time, H/Pd atomic ratio were obtained by theoretical fitting of the near-edge region of the absorption spectra (XANES) and compared with volumetric measurements. (paper)