Search

Flexible metal-organic frameworks (MOFs) are capable of changing their crystal structure as a function of external stimuli such as pressure, temperature, and type of adsorbed guest species. DUT-49 is the first MOF exhibiting structural transitions accompanied by the counterintuitive phenomenon of negative gas adsorption (NGA). Here, we present high pressure in situ ¹²⁹Xe NMR spectroscopic studies of a novel isoreticular MOF family based on DUT-49. These po-rous materials differ only in the length of their organic linkers causing changes in pore size and elasticity. The series encompasses both, purely microporous materials as well as materials with both, micropores and small mesopores. The chemical shift of adsorbed xenon depends on xenon-wall interactions and thus, on the pore size of the material. The xenon adsorption behavior of the different MOFs can be observed over the whole range of relative pressure. Chemical shift adsorption/desorption isotherms closely resembling the conventional, uptake-measurement based isotherms were obtained at 237 K where all materials are rigid. The comparable chemical environment for adsorbed xenon in these isoreticular MOFs allows establishing a correlation between the chemical shift at a relative pressure of p/p₀ = 1.0 and the mean pore diameter. Furthermore, the xenon adsorption behavior of the MOFs is studied also at 200 K. Here, struc-tural flexibility is found for DUT 50, a material with an even longer linker than the previously known DUT-49. Its structural transitions are monitored by ¹²⁹Xe NMR spectroscopy. This compound is the second known MOF showing the phenomenon of negative gas adsorption. Further increase in the linker length results in DUT-151, a material with interpenetrated network topology. In situ ¹²⁹Xe NMR spectroscopy proves that this material exhibits another type of flexibility compared to DUT-49 and DUT-50. Further surprising observations are made for DUT-46. Volumetric xenon adsorption measurements show that this non-flexible microporous material does not exhibit any hysteresis. In contrast, in situ ¹²⁹Xe NMR spectroscopically detected xenon chemical shift isotherms exhibit a hysteresis even after longer equilibration times than in the volumetric experiments. This indicates kinetically hindered re-distribution processes and long-lived metastable states of adsorbed xenon within the MOF persisting at the time scale of hours or longer.

Nach Jahren fortschreitender europäischer Integration, geprägt vom permissive consensus, rückt – durch den Aufstieg rechtspopulistischer Parteien – die Ablehnung gegenüber der Europäischen Union in den Fokus wissenschaftlicher Debatten. Während überwiegend von Euro- oder Europaskeptizismus die Rede ist, fasst dieser Beitrag die Ablehnung gegenüber dem europäischen Integrationsprojekt unter dem präziseren Begriff des EU-Skeptizismus zusammen. In diesem spiegeln sich die drei Kernelemente des Rechtspopulismus wider: Populismus, Nativismus und Autoritarismus. Mittels einer Diskursanalyse werden in der vorliegenden Arbeit die Ausprägungen des EU-Skeptizismus des Front National (FN, Frankreich), der Freiheitlichen Partei Österreichs (FPÖ) und der Partij voor de Vrijheid (PVV, Niederlande) im Zeitraum von 2010 bis Beginn 2018 untersucht. Für die Einordnung und Vergleichbarkeit des EU-Skeptizismus der rechtspopulistischen Parteien wurde ein Kriterienkatalog erarbeitet, der auf die Untersuchung weiterer Parteien übertragbar ist. Die Ergebnisse zeigen, dass der EU-Skeptizismus nicht nur ideologisch, sondern auch strategisch motiviert ist. Die Aussicht auf Regierungsverantwortung beziehungsweise die faktische Regierungsbeteiligung schwächt den bestehenden EU-Skeptizismus ab. Während letzteres auf die FPÖ zutrifft, zeichnen sich PVV und FN durch einen konstant harten EU-Skeptizismus (in Anlehnung an die Unterscheidung der Kategorien hard und soft von Taggart u. Szczerbiak 2008) aus. Wenngleich sich der harte EUSkeptizismus rechter Parteien durch die komplizierten Brexitverhandlungen abschwächen könnte, wird weicher EU-Skeptizismus über den geplanten Austritt des Vereinigten Königreichs hinaus Bestand haben., After years of progressive European integration marked by the permissive consensus, the rise of right-wing populist parties has put the opposition towards the European Union at the center of scientific debate. Instead of referring to the widely used but vague term of Euroscepticism, this paper summarizes the rejection of the European integration project under the more precise term of EU-scepticism. EU-scepticism reflects the three core elements of right-wing populism: populism, nativism and authoritarianism. By conducting a discourse analysis, the characteristics of EU-scepticism of the Front National (FN, France), the Austrian Freedom Party (FPÖ) and the Party for Freedom (PVV, Netherlands) will be examined for the period from 2010 to the beginning of 2018. To classify and compare EU-scepticism of right-wing populist parties, a list of criteria has been developed, which can be used for further research. The results show that EU-scepticism is not only ideologically but also strategically motivated. The prospect of government responsibility or government participation weakens existing EU-scepticism. While the latter applies to the FPÖ, the PVV and FN are characterized by a consistently hard EU-scepticism (based on the distinction between the hard and soft categories established by Taggart u. Szczerbiak 2008). Although hard EU-scepticism could weaken as a result of the complicated Brexit negotiations, soft EU-scepticism will remain a key theme of right-wing parties – even after the exit of the United Kingdom.

Exploring the role of surface hydrophilicity of non-precious metal N-doped carbon electrocatalysts in electrocatalysis is challenging. Herein we discover an ultra-hydrophilic non-precious carbon electrocatalyst, showing enhanced catalysis efficiency on both gravimetric and areal basis for oxygen reduction reaction due to a high dispersion of active centres.

A new mesoporous MOF, Zn4O(bpdc)(btctb)4/3 (DUT-32), containing linear ditopic (bpdc2−; 4,4'-biphenylenedicarboxylic acid) and tritopic (btctb3−; 4,4',4''-[benzene-1,3,5-triyltris(carbonylimino)]tris-benzoate) linkers, was synthesised. The highly porous solid has a total pore volume of 3.16 cm3 g−1 and a specific BET surface area of 6411 m2 g−1, adding this compound to the top ten porous materials with the highest BET surface area.