We show that the activity and selectivity of Cu catalyst can be promoted by a Zr-based metal-organic framework (MOF), ZrO(OH)(BDC) (BDC = 1,4-benzenedicarboxylate), UiO-66, to have a strong interaction with Zr oxide [ZrO(OH)(-CO)] secondary building units (SBUs) of the MOF for CO hydrogenation to methanol. These interesting features are achieved by a catalyst composed of 18 nm single Cu nanocrystal (NC) encapsulated within single crystal UiO-66 (Cu⊂UiO-66). The performance of this catalyst construct exceeds the benchmark Cu/ZnO/AlO catalyst and gives a steady 8-fold enhanced yield and 100% selectivity for methanol. The X-ray photoelectron spectroscopy data obtained on the surface of the catalyst show that Zr 3d binding energy is shifted toward lower oxidation state in the presence of Cu NC, suggesting that there is a strong interaction between Cu NC and Zr oxide SBUs of the MOF to make a highly active Cu catalyst.

A theoretical model supported by experimental results explains the dependence of the Raman scattering signal on the evolution of structural parameters along the amorphization trajectory of polycrystalline graphene systems.Four parameters rule the scattering efficiencies, two structural and two related to the scattering dynamics. With the crystallite sizes previously defined from X-ray diffraction and microscopy experiments, the three other parameters (the average grain boundaries width, the phonon coherence length, and the electron coherence length) are extracted from the Raman data with the geometrical model proposed here. The broadly used intensity ratio between

We report the direct experimental observation of the semiconductor-metal transition in single-wall carbon nanotubes (SWNTs) induced by compression with the tip of an atomic force microscope. This transition is probed via electric force microscopy by monitoring SWNT charge storage. Experimental data show that such charge storage is different for metallic and semiconducting SWNTs, with the latter presenting a strong dependence on the tip-SWNT force during injection. Ab initio calculations corroborate experimental observations and their interpretation.

The growth of the dental implant market increases the concern regarding the quality, efficiency, and lifetime of dental implants. Titanium and its alloys are dominant materials in this field thanks to their high biocompatibility and corrosion resistance, but they possess a very low wear resistance. Besides problems related to osteointegration and bacterial infections, tribocorrosion phenomena being the simultaneous action between corrosion and wear, are likely to occur during the lifetime of the implant. Therefore, tribocorrosion resistant surfaces are needed to guarantee the preservation of dental implants. This work focused on the incorporation of magnesium, together with calcium and phosphorous, in the structure of titanium oxide films produced by micro-arc oxidation (MAO). The characterization of morphology, chemical composition, and crystalline structure of the surfaces provided important insights leading to 1) a better understanding of the oxide film growth mechanisms during the MAO treatment; and 2) a better awareness on the degradation process during tribocorrosion tests. The addition of magnesium was shown to support the formation of rutile which improves the tribocorrosion properties of the surfaces.

COF‐300, an imine‐linked, crystalline, and microporous covalent organic framework, modified by coordination of Pd(OAc)2 to its walls, afforded a hybrid material, Pd(OAc)2@COF‐300, which was used as an efficient heterogeneous catalyst for cross‐coupling reactions. This material showed excellent catalytic activity for the phosphine‐free Suzuki–Miyaura, Heck, and Sonogashira cross‐coupling reactions with low palladium loadings (0.1 mol % Pd). X‐ray photoelectron spectroscopy analysis of the catalyst after the reaction showed that PdII is converted to Pd0, which is trapped within the COFs nanopores. This was confirmed by high‐resolution transmission electron microscopy. Moreover, promising results were obtained using Pd(OAc)2@COF‐300 under continuous‐flow conditions for a Suzuki–Miyaura cross‐coupling reaction.