Defibrillation of soft porous metal-organic frameworks with electric fields

Abstract

Gas transport through metal-organic framework membranes (MOFs) was switched in situ by applying an external electric field (E-field). The switching of gas permeation upon E-field polarization could be explained by the structural transformation of the zeolitic imidazolate framework ZIF-8 into polymorphs with more rigid lattices. Permeation measurements under a direct-current E-field poling of 500 volts per millimeter showed reversibly controlled switching of the ZIF-8 into polar polymorphs, which was confirmed by x-ray diffraction and ab initio calculations. The stiffening of the lattice causes a reduction in gas transport through the membrane and sharpens the molecular sieving capability. Dielectric spectroscopy, polarization, and deuterium nuclear magnetic resonance studies revealed low-frequency resonances of ZIF-8 that we attribute to lattice flexibility and linker movement. Upon E-field polarization, we observed a defibrillation of the different lattice motions.

Aqueous Stable Gold Nanostar/ZIF‐8 Nanocomposites for Light‐Triggered Release of Active Cargo Inside Living Cells

“…( Figure 1F), characteristic of microporous materials,w ith Brunauer-Emmett-Teller-specific surface areas (S BET )o f 1800, 1570, 1260, 850, and 220 m 2 g À1 ,r espectively.N ormalization of S BET by the porous ZIF-8 weight shows no significant difference between ZIF-8 and the NCs,indicating that the ZIF-8 shell shares the same textural properties as the pristine ZIF-8 (Table S6). In fact, although the estimated HOE dimensions (18.5 4.1 4.1 )a re slightly larger than the accessible windows of ZIF-8 ( % 3.6 ), [20] the potential HOE rearrangement and the flexibility of ZIF-8 [21] support the location of HOE within the pores,w hich is consistent with the SERS results. Importantly, corrected surfaces indicate that PMA, besides providing an outer coating for the NPs,p artially fills NC-PMA (S BET % 1440 m 2 g À1 ), which is in agreement with the results found by the fluorescence measurements ( % 60 %H OE loss after PMA, final corrected S BET % 470 m 2 g À1 ).…”

Quo Vadis, MOF?

“…The complexity of the problem is demonstrated in , which shows that it is possible to tune the linker swing motion, and thus, the adsorption properties of ZIF‐90 by manipulating the terminal group rotation. Just recently the framework flexibility could be exploited to switch the MOF lattice by light or electric field . Another spectacular phenomenon linked to framework flexibility is negative gas adsorption found by Kaskel for DUT‐49 at 111 K .…”

Dynamic Studies on Kinetic H2/D2 Quantum Sieving in a Narrow Pore Metal–Organic Framework Grown on a Sensor Chip

“…The exact impact of the distortion of flexible MOFs in the presence of strong electric fields is not taken into account by the molecular dynamics calculations, nor have we experimentally investigated this effect by varying the SAW power, so far. Electric fields can exert a strong influence on the mechanical properties of soft materials such as metal–organic frameworks, as can be seen in a previous publication …”