Flexible metal-organic frameworks that show reversible guest-induced phase transitions between closed and open pore phases have enormous potential for highly selective, energy-efficient gas separations. Here, we present the gate-opening process of DUT-8(Ni) that selectively responds to D 2 , whereas no response is observed for H 2 and HD. In situ neutron diffraction directly reveals this pressure-dependent phase transition. Low-temperature thermal desorption spectroscopy measurements indicate an outstanding D 2 -over-H 2 selectivity of 11.6 at 23.3 K, with high D 2 uptake. First-principles calculations coupled with statistical thermodynamics predict the isotope-selective gate opening, rationalized by pronounced nuclear quantum effects. Simulations suggest DUT-8(Ni) to remain closed in the presence of HT, while it also opens for DT and T 2 , demonstrating gate opening as a highly effective approach for isotopolog separation.

Flexible metal–organic frameworks (MOFs) undergo reversible structural transformations triggered by external stimuli. An interesting feature of some MOFs is their ability to flex in response to specific guests, which can enable selective separation. Here, we introduce MUF-15-OMe ([Co6(μ3-OH)2(ipa-OMe)5(H2O)4]), a variant of MUF-15 that comprises hexanuclear cobalt­(II) clusters connected by 5-methoxyisophthalate (ipa-OMe) ligands. MUF-15 itself has isophthalate linkers and is inflexible upon uptake of common gases. On the other hand, MUF-15-OMe flexes upon the uptake of gases such as CO2 and C2 hydrocarbons at pressures less than 1 bar, as revealed by distinct steps in its gas adsorption isotherms. Computational analysis showed that the underlying mechanism involves partial detachment of one of the carboxyl groups of the framework linkers. The gas pressure required to induce framework dynamics can be tuned by replacing some of the ipa-OMe by isophthalate ligands in multivariate frameworks. The flexing of MUF-15-OMe opens up space for the adsorption of specific additional gas molecules. This enhances the separation of CO2 and N2 and enables the differentiation of H2 and D2 by quantum sieving. By providing a clear illustration of how flexibility allows the discrimination of gas mixtures, this study underpins the use of dynamic MOFs for challenging separations.

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We present a new experimental approach to investigate the magnetic properties of the anisotropic heavy-fermion system YbRh 2 Si 2 as a function of crystallographic orientation. Angle-dependent electron spin resonance (ESR) measurements are performed at a low temperature of 1.6 K and at an ESR frequency of 4.4 GHz utilizing a superconducting planar microwave resonator in a 4 He-cryostat in combination with in-situ sample rotation. The obtained ESR g-factor of YbRh 2 Si 2 as a function of the crystallographic angle is consistent with results of previous measurements using conventional ESR spectrometers at higher frequencies and fields. Perspectives to implement this experimental approach into a dilution refrigerator and to reach the magnetically ordered phase of YbRh 2 Si 2 are discussed.

Although traffic exhaust emissions in Europe have been drastically reduced, airborne particle emissions caused by brakes and tires are still increasing with the number of vehicles. The measurement of non-exhaust emissions is an emerging technological challenge. We present a custom measurement setup to investigate the brake- and tire-wear emissions of an in-use battery electric vehicle. A separate brake housing and HEPA ventilation enabled airborne brake wear emissions to be measured under realistic conditions without external influences. The emission tests on a chassis dynamometer included particle number concentrations and particle size distribution for diameters of 4 nm to 10 μm. Emission indices were determined for three driving cycles: WLTC Class 3b, WLTC Brake Part 10, and a real driving cycle. Further investigations focused on emission control through regenerative braking and brake coating. Driving with regenerative braking reduced emissions by up to 89.9%, which related to the concentration of particles in the ultrafine/fine size range. Hard-metal brake coating led to a further significant reduction in emissions of up to 78.9%. The results point the way to future RDE measurement of non-exhaust emissions and show the potential of regenerative braking and brake coating to reduce airborne brake wear emissions.