1,846 research outputs found
On the use of the IAST method for gas separation studies in porous materials with gate-opening behavior
Highly flexible nanoporous materials, exhibiting for instance gate opening or
breathing behavior, are often presented as candidates for separation processes
due to their supposed high adsorption selectivity. But this view, based on
"classical" considerations of rigid materials and the use of the Ideal Adsorbed
Solution Theory (IAST), does not necessarily hold in the presence of framework
deformations. Here, we revisit some results from the published literature and
show how proper inclusion of framework flexibility in the osmotic thermodynamic
ensemble drastically changes the conclusions, in contrast to what intuition and
standard IAST would yield. In all cases, the IAST method does not reproduce the
gate-opening behavior in the adsorption of mixtures, and may overestimates the
selectivity by up to two orders of magnitude
Measurement-induced qubit state mixing in circuit QED from up-converted dephasing noise
We observe measurement-induced qubit state mixing in a transmon qubit
dispersively coupled to a planar readout cavity. Our results indicate that
dephasing noise at the qubit-readout detuning frequency is up-converted by
readout photons to cause spurious qubit state transitions, thus limiting the
nondemolition character of the readout. Furthermore, we use the qubit
transition rate as a tool to extract an equivalent flux noise spectral density
at f ~ 1 GHz and find agreement with values extrapolated from a
fit to the measured flux noise spectral density below 1 Hz.Comment: 5 pages, 4 figures. Final journal versio
Stress-Based Model for the Breathing of MetalâOrganic Frameworks
International audienceGas adsorption in pores of flexible metalâorganic frameworks (MOF) induces elastic deformation and structural transitions associated with stepwise expansion and contraction of the material, known as breathing transitions between large pore (lp) and narrow pore (np) phases. We present here a simple yet instructive model for the physical mechanism of this enigmatic phenomenon considering the adsorption-induced stress exerted on the material as a stimulus that triggers breathing transitions. The proposed model implies that the structural transitions in MOFs occur when the stress reaches a certain critical threshold. We showcase this model by drawing on the example of Xe adsorption in MIL-53 (Al) at 220 K, which exhibits two consecutive hysteretic breathing transitions between lp and np phases. We also propose an explanation for the experimentally observed coexistence of np and lp phases in MIL-53 materials
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