Using a novel layer-by-layer approach we have deposited metal−organic open frameworks (MOFs) based on benzenetricarboxylic acid ligands and Cu(II)-ions on a COOH-terminated organic surface. The deposited layers were characterized using a number of surface analysis techniques. XRD measurements show that the MOFs deposited using this method have the same bulk structure of HKUST-1.

We report the synthesis of layered [Zn(2)(bdc)(2)(H(2)O)(2)] and [Cu(2)(bdc)(2)(H(2)O)(2)] (bdc = benzdicarboxylate) metal-organic frameworks (MOF) carried out using the liquid-phase epitaxy approach employing self-assembled monolayer (SAM) modified Au-substrates. We obtain Cu and Zn MOF-2 structures, which have not yet been obtained using conventional, solvothermal synthesis methods. The 2D Cu(2+) dimer paddle wheel planes characteristic for the MOF are found to be strictly planar, with the planes oriented perpendicular to the substrate. Intercalation of an organic dye, DXP, leads to a reversible tilting of the planes, demonstrating the huge potential of these surface-anchored MOFs for the intercalation of large, planar molecules.

We report on the microscopic structure of water at sub-and supercritical conditions studied using X-ray Raman spectroscopy, ab initio molecular dynamics simulations, and density functional theory. Systematic changes in the X-ray Raman spectra with increasing pressure and temperature are observed. Throughout the studied thermodynamic range, the experimental spectra can be interpreted with a structural model obtained from the molecular dynamics simulations. A spatial statistical analysis using Ripley's K-function shows that this model is homogeneous on the nanometer length scale. According to the simulations, distortions of the hydrogenbond network increase dramatically when temperature and pressure increase to the supercritical regime. In particular, the average number of hydrogen bonds per molecule decreases to ≈0.6 at 600°C and p = 134 MPa.supercritical water | water structure | X-ray scattering | X-ray scattering spectroscopy

Herein, we explore the effect of different types of osmolytes on the high-pressure stability and tertiary structure of a well-characterized monomeric protein, staphylococcal nuclease (SNase). Changes in the denaturation pressure and the radius of gyration are obtained in the presence of different concentrations of trimethylamine N-oxide (TMAO), glycerol and urea. To reveal structural changes in the protein upon compression at various osmolyte conditions, small-angle X-ray scattering (SAXS) experiments were carried out. To this end, a new high-pressure cell suitable for high-precision SAXS studies at synchrotron sources was built, which allows one to carry out scattering experiments up to maximum pressures of about 7 kbar. Our data clearly indicate that the osmolytes that stabilize proteins against temperature-induced unfolding drastically increase their pressure stability and that the elliptically shaped curve of the pressure-temperature-stability diagram of proteins is shifted to higher temperatures and pressures with increasing osmolyte concentration. A drastic stabilization is observed for the osmolyte TMAO, which exhibits not only a significant stabilization against temperature-induced unfolding, but also a particularly strong stabilization of the protein against pressure. In fact, such findings are in accordance with in vivo studies (for example P. J. Yancey, J. Exp. Biol. 2005, 208, 2819-2830), where unusually high TMAO concentrations in some deep-sea animals were found. Conversely, chaotropic agents such as urea have a strong destabilizing effect on both the temperature and pressure stability of the protein. Our data also indicate that sufficiently high TMAO concentrations might be able to largely offset the destabilizing effect of urea. The different scenarios observed are discussed in the context of recent experimental and theoretical studies.

The pillared-layered metal−organic framework compounds M 2 (BME-bdc) 2 (dabco) (M 2+ = Zn 2+ , Co 2+ , Ni 2+ , Cu 2+ ; BME-bdc 2− = 2,5-bis(2-methoxyethoxy)-1,4-benzenedicarboxylate; dabco = diazabicyclo[2.2.2]octane) exhibit structural flexibility and undergo guest and temperature-induced reversible phase transitions between a narrow pore (np) and a large pore (lp) form. These transitions were analyzed in detail by powder X-ray diffraction ex and in situ, isothermal gas adsorption measurements and differential scanning calorimetry. The threshold parameters (gas pressure or temperature), the magnitude of the phase transitions (volume change) as well as their transition enthalpies are strikingly dependent on the chosen metal cation M 2+ . This observation is assigned to the different electronic structures and ligand field effects on the coordination bonds. Accordingly, in situ powder X-ray diffraction measurements as a function of CO 2 pressure reveal different mechanisms for the np to lp phase transition during CO 2 adsorption.

Flexible metal-organic frameworks (MOFs) are structurally flexible, porous, crystalline solids that show a structural transition in response to a stimulus. If MOF-based solid-state and microelectronic devices are to be capable of leveraging such structural flexibility, then the integration of MOF thin films into a device configuration is crucial. Here we report the targeted and precise anchoring of Cu-based alkylether-functionalised layered-pillared MOF crystallites onto substrates via stepwise liquid-phase epitaxy. The structural transformation during methanol sorption is monitored by in-situ grazing incidence X-ray diffraction. Interestingly, spatially-controlled anchoring of the flexible MOFs on the surface induces a distinct structural responsiveness which is different from the bulk powder and can be systematically controlled by varying the crystallite characteristics, for instance dimensions and orientation. This fundamental understanding of thin-film flexibility is of paramount importance for the rational design of MOF-based devices utilising the structural flexibility in specific applications such as selective sensors.

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In contrast to all known shape memory polymers, the melting temperature of crystals in shape memory natural rubber (SMNR) can be greatly manipulated by the application of external mechanical stress. As shown previously, stress perpendicular to the prior programming direction decreases the melting temperature by up to 40 K. In this study, we investigated the influence of mechanical stress parallel to prior stretching direction during programming on the stability of the elongation-stabilizing crystals. It was found that parallel stress stabilizes the crystals, which is indicated by linear increase of the trigger temperature by up to 17 K. The crystal melting temperature can be increased up to 126.5 °C under constrained conditions as shown by X-ray diffraction measurements.