1,3,3-Trimethylindolino-6'-nitrobenzopyrylospiran (SP-1) as an example of a photoswitchable spiropyran was loaded into the pores of different prototypical metal-organic frameworks, namely MOF-5, MIL-68(In), and MIL-68(Ga), by a vapor-phase process. The successful incorporation in the pores of the MOF was proven by X-ray powder diffraction, and the amount of the embedded photoswitchable guest was determined by X-ray photoelectron spectroscopy and elemental analysis. In contrast to the sterically hindered crystalline state, SP-1 embedded in solid MOF hosts shows photoswitching under irradiation with UV light from the spiropyran to its merocyanine form with a nearly complete photoisomerization. Switching can be reversed by heat treatment. These switching properties were confirmed by means of UV/vis and IR spectroscopy. Remarkably, the embedded guest molecules show photoswitching and absorption properties similar to those in the dissolved state, so that MOFs might be considered as "solid solvents" for photoswitchable spiropyrans. In contrast to that, embedment of SP-1 in the smaller pores of MIL-53(Al) was not successful. SP-1 is mainly adsorbed on the surfaces of the MIL-53(Al) particles, which also leads to photoswitching properties.

Conductive metal–organic frameworks (MOFs) as well as smart, stimuli‐responsive MOF materials have attracted considerable attention with respect to advanced applications in energy harvesting and storage as well as in signal processing. Here, the conductance of MOF films of type UiO‐67 with embedded photoswitchable nitro‐substituted spiropyrans was investigated. Under UV irradiation, the spiropyran (SP) reversibly isomerizes to the open merocyanine (MC) form, a zwitterionic molecule with an extended conjugated π‐system. The light‐induced SP–MC isomerization allows for remote control over the conductance of the SP@UiO‐67 MOF film, and the conductance can be increased by one order of magnitude. This research has the potential to contribute to the development of a new generation of photoelectronic devices based on smart hybrid materials.

Highly conductive solid electrolytes are crucial to the development of efficient all-solid-state batteries. Meanwhile, the ion conductivities of lithium solid electrolytes match those of liquid electrolytes used in commercial Li ion batteries. However, concerns about the future availability and the price of lithium made Na ion conductors come into the spotlight in recent years. Here we present the superionic conductor Na Sn PS , which possesses a room temperature Na conductivity close to 4 mS cm , thus the highest value known to date for sulfide-based solids. Structure determination based on synchrotron X-ray powder diffraction data proves the existence of Na vacancies. As confirmed by bond valence site energy calculations, the vacancies interconnect ion migration pathways in a 3D manner, hence enabling high Na conductivity. The results indicate that sodium electrolytes are about to equal the performance of their lithium counterparts.

Several metal-organic framework compounds (MOF-5, MIL-68(Ga), MIL-68(In), MIL-53(Al)) were loaded with azobenzene (AZB), as confirmed by XRPD measurements and elemental analysis. By IR spectroscopy, it was shown that the light-induced trans/cis isomerization of AZB in these hybrid host-guest compounds is improved compared to that of solid AZB. A population of the excited cis state up to 30% has been obtained for AZB0.66@MIL-68(In). However, no light-induced trans/cis isomerization was observed for AZB0.5@MIL-53(Al). Structural models obtained from high-resolution synchrotron powder diffraction data show that AZB molecules are densely packed within the channels of MIL-53(Al) so that no trans/cis isomerization can occur. A different situation was observed for AZB in the larger channels of MIL-68(Ga). Thus, this investigation shows the influence of the host material on the switching behavior of the embedded AZB molecules.

We report on the first quaternary selenide-based Na+ superionic solid electrolyte, Na11.1Sn2.1P0.9Se12 (further denoted as NaSnPSe), which shows virtually the same room temperature Na+ ion conductivity (3.0 mS/cm) as the current record holder for sulfide-based systems, Na11Sn2PS12 (denoted as NaSnPS), but with a considerably lower activation energy of 0.30 eV. Both electrolytes belong to the currently highly topical class of solids comprising group I, IV, V, and VI atoms, which we summarize as 1–4–5–6 electrolytes. Herein, they are compared to each other with regard to their structural characteristics and the resulting ion transport properties. The lower activation energy of Na+ ion transport in NaSnPSe is well in line with the results of speed of sound measurements, Raman spectroscopy, bond-valence site energy calculations, and molecular dynamics simulations, all of which point to a lower lattice rigidity and to weaker Na–chalcogen interactions as compared to NaSnPS.