Hydrogels are fabricated from CdSe/CdS seeded nanorod building blocks by the addition of hydrogen peroxide and converted to aerogels by supercritical drying. The aerogels show higher photoluminescence quantum yields and longer lifetimes than the hydrogels and the nanoparticle solutions. A model for this observation is derived.

Metal–organic frameworks (MOFs) with an exceptionally large pore volume and inner surface area are perfect materials for loading with intelligent guest molecules. First, an ultrathin 200 nm high-flux UiO-67 layer deposited on a porous α-Al2O3 support by solvothermal growth has been developed. This neat UiO-67 membrane is then used as a host material for light-responsive guest molecules. Azobenzene (AZB) is loaded in the pores of the UiO-67 membrane. From adsorption measurements, we determined that the pores of UiO-67 are completely filled with AZB and, thereby, steric hindrance inhibits any optical switching. After in situ thermally controlled desorption of AZB from the membrane, AZB can be switched and gas permeation changes are observed, yielding an uncomplicated and effective smart material with remote controllable gas permeation. The switching of AZB in solution and inside the host could be demonstrated by ultraviolet–visible spectroscopy. Tracking the completely reversible control over the permeance of CO2 and the H2/CO2 separation through the AZB-loaded UiO-67 layer is possible by in situ irradiation and permeation. Mechanistic investigations show that a light-induced gate opening and closing takes place. A remote controllable host–guest, ultrathin smart MOF membrane is developed, characterized, and applied to switch the gas composition by external stimuli.

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The 3D metal-organic framework (MOF) structure UiO-66 [ZrO(OH)(bdc)], featuring triangular pores of approximately 6 Å, has been successfully prepared as a thin supported membrane layer with high crystallographic orientation on ceramic α-AlO supports. The adhesion of the MOF layer to the ceramic support was investigated in different taxing conditions. Furthermore, by coating this UiO-66 membrane with a thin polyimide (Matrimid) top layer, we prepared a multilayer composite. Said membranes have been evaluated in the separation of hydrogen (H) from different binary mixtures at room temperature. H as the smallest molecule (2.9 Å) should pass the UiO-66 membrane preferably since the kinetic diameters of all the other gases under study are larger. The gas mixture separation factors for the neat UiO-66 membrane were indeed found to be H/CO = 5.1, H/N = 4.7, H/CH = 12.9, H/CH = 22.4, and H/CH = 28.5. The coating with Matrimid led to a sharp cutoff for gases with kinetic diameters greater than 3.7 Å, resulting in increased separation performance.

MIL-96(Al) layers were prepared as supported metal-organic frameworks membrane via reactive seeding using the α-alumina support as the Al source for the formation of the MIL-96(Al) seeds. Depending on the solvent mixture employed during seed formation, two different crystal morphologies, with different orientation of the transport-active channels, have been formed. This crystal orientation and habit is predefined by the seed crystals and is kept in the subsequent growth of the seeds to continuous layers. In the gas separation of an equimolar H2/CO2 mixture, the hydrogen permeability of the two supported MIL-96(Al) layers was found to be highly dependent on the crystal morphology and the accompanied channel orientation in the layer. In addition to the neat supported MIL-96(Al) membrane layers, mixed-matrix membranes (MMMs, 10 wt % filler loading) as a composite of MIL-96(Al) particles as filler in a continuous Matrimid polymer phase have been prepared. Five particle sizes of MIL-96(Al) between 3.2 μm and 55 nm were synthesized. In the preparation of the MIL-96(Al)/Matrimid MMM (10 wt % filler loading), the following preparation problems have been identified: The bigger micrometer-sized MIL-96(Al) crystals show a trend toward sedimentation during casting of the MMM, whereas for nanoparticles aggregation and recrystallization to micrometer-sized MIL-96(Al) crystals has been observed. Because of these preparation problems for MMM, the neat supported MIL-96(Al) layers show a relatively high H2/CO2 selectivity (≈9) and a hydrogen permeance approximately 2 magnitudes higher than that of the best MMM.