Consideration for the correlation between basicity of oxide glasses and chemical shift of O1s binding energy in XPS

Binding energy of O1s core electron measured in XPS is a candidate to determine new scale of Lewis basicity of oxide ion in glass. Some mathematical expressions for the basicity or XPS chemical shift, such as charge parameter and optical basicity, are compared with experimental O1s binding energy in binary alkali oxide glasses. The expressions so far in use need some modification in parameters. A new empirical expression introduced in this paper gives new concept and universal scale of basicity

酸化物ガラスの塩基度と XPS による O1s 化学シフトの相関に関する考察

O1s binding energy measured by X-ray photoelectron spectroscopy (XPS) is candidate as a new tool to determine a new scale of Lewis basicity of oxide ions in glass. Some mathematical expressions for the basicity or XPS chemical shift, such as charge parameter and optical basicity, were compared with the experimental O1s binding energy in binary alkali oxide glasses. The expressions so far in use needed some modification in parameters. A new empirical expression introduced in this paper gives a new concept and universal scale of basicity

Effect of building block transformation in covalent triazine‐based frameworks for enhanced CO2 uptake and metal‐free heterogeneous catalysis

Invited for the cover of this issue is the group of Pascal Van Der Voort at the University of Ghent and colleagues at Technische Universitat Berlin. The image depicts the covalent triazine frameworks reported in the manuscript for the sorption of CO2 and also in metal-free catalysis. Read the full text of the article at 10.1002/chem.201903926

Lewis Basicity of Nitrogen-Doped Graphite Observed by CO2 Chemisorption

The characteristics of CO2 adsorption sites on a nitrogen-doped graphite model system (N-HOPG) were investigated by X-ray photoelectron and absorption spectroscopy and infrared reflection absorption spectroscopy. Adsorbed CO2 was observed lying flat on N-HOPG, stabilized by a charge transfer from the substrate. This demonstrated that Lewis base sites were formed by the incorporation of nitrogen via low-energy nitrogen-ion sputtering. The possible roles of twofold coordinated pyridinic N and threefold coordinated valley N (graphitic N) sites in Lewis base site formation on N-HOPG are discussed. The presence of these nitrogen species focused on the appropriate interaction strength of CO2 indicates the potential to fine-tune the Lewis basicity of carbon-based catalysts

Die Wechselwirkung von N3F mit Lewis-Säuren und HF. N3F als möglicher Vorläufer für die Synthese von N3+-Salzen

Triazadienyl fluoride, N3F, forms stable adducts with BF3 and AsF5 at low temperatures, as demonstrated by infrared measurements. The Lewis acids are bonded to the Nα-atom of N3F, as deduced from the data for 15N-isotopically enriched N3F. The basicity of N3F is comparable to that of ethine and ethene, according to the HF stretching frequency of the N3F/HF complex isolated in an argon matrix. Despite the low NF bond energy (< 150 kJ/mol), abstraction of the fluoride ion and formation of an N3+ salt was not possible. The different behavior of N3F and ClN3 towards Lewis acids is discussed

Factors affecting the extent of branching in fischertropsch synthesis products with iron-based catalysts

Branched products are mainly formed during secondary isomerization reactions, and not in the main synthesis reaction itself. The extent of branching is a function of the catalyst formulation. High acidity and a low hydrogenation strength of the catalyst (normally found in catalysts with a high basicity) favour branching. The latter can be explained by the fact that the rate of skeletal isomerization of alkenes is much higher than the rate of hydrogenation. If the former rate is higher than the latter, hydrogenation will take place rapidly before any isomerization can occur. Little variation with time on stream is observed in the extent of branching with non-acidic catalysts. Acidic catalysts yield initially a much more branched product, the extent of which decreases with time on stream, to eventually reach levels only marginally higher than those observed with non-acidic catalysts. The extent of branching is different for products with different carbon numbers. It does not follow a random probability pattern, as results from a hydrocarbon synthesis in which single carbon units are linked to the growing chains at random places, but rather a pattern which depends on the hydrogenation strength of the catalyst used. With low hydrogenation strength catalysts, branching occurs preferentially in the lighter products. Branching is favoured in the heavier products when higher hydrogenation strength catalysts are used. This is explained in terms of the higher surface mobility of lighter products