Supported ZIF and mixed matrix membranes for pervaporation and permeation

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MOF membrane synthesis in the confined space of a vertically aligned LDH network

MOF membranes have gained widespread attention due to their unprecedented gas separation performance. Relying on physical interactions, we successfully deposited MOF seeds on a substrate modified with a network of vertically aligned LDH walls before secondary growth of the MOF layer. ZIF-8 membranes thus prepared show considerable H-2 permeance with high H-2-CH4 selectivity. This approach is in general suitable for the deposition of nanoparticles on solid surface and their subsequent growth into a dense layer.EC/FP7/263007Alexander von Humboldt FoundationFP7-NMP-2010-LARGE-4, Nr. 26300

The influence of crystallographic orientation on the wetting of silicon on quartz single crystals

Dynamic hexagonal spreading patterns of small silicon droplets on the basal plane (001) of quartz were observed by video microscopy. A detailed analysis of the hexagonal triple line demonstrates that the patterns show slight chiral distortions that can be attributed to the screw axis of the substrate crystal. This article reveals the detailed influence of crystal symmetry on the anisotropy of reactive wetting. In this context, a first discussion about the interplay of wetting and etching of a crystal is provided

Polydopamine-based synthesis of a zeolite imidazolate framework ZIF-100 membrane with high H2/CO2 selectivity

A highly permselective ZIF-100 molecular sieve membrane has been prepared on a polydopamine (PDA)-modified support. Attributed to the formation of strong covalent and non-covalent bonds between PDA and ZIF-100, the ZIF-100 nutrients are attracted and bound to the support surface, thus promoting the growth of well-intergrown and phase-pure ZIF-100 membranes. The developed ZIF-100 membranes show high H2/CO2 selectivity due to the outstanding CO2 adsorption capacity of ZIF-100.EC/FP7/263007FP7-NMP-2010-LARGE-4/263007Chinese Academy of Science Visiting Professorship for Senior International Scientists/2013T1G0047China Postdoctoral Science Foundation/2014M560663)Fundamental Research Funds for the Central Universities/2014ZB001

Rotational and Translational Motion of Benzene in ZIF‑8 Studied by ²H NMR: Estimation of Microscopic Self-Diffusivity and Its Comparison with Macroscopic Measurements

In relation to unique properties of metal–organic framework (MOF) ZIF-8 to adsorb and separate hydrocarbons with kinetic diameters notably larger than the entrance windows of the porous system of this microporous material, the molecular dynamics of benzene adsorbed on ZIF-8 has been characterized and quantified with ²H nuclear magnetic resonance. We have established that within the ZIF-8 cage the benzene molecule undergoes fast rotations, hovering in the symmetric potential of the spherical cage and relatively slow isotropic reorientations by collisions with the walls. Benzene performs also translational jump diffusion between neighboring cages characterized by an activation barrier <i>E</i>_D = 38 kJ mol^–1 and a pre-exponential factor τ_D0 = 4 × 10^–10 s. This microscopic measurement of benzene mobility allows us to estimate the self-diffusion coefficient for benzene in ZIF-8 (<i>D</i>⁰_self ≈ 4 × 10^–16 m² s^–1 at <i>T</i> = 323 K). Macroscopic measurements of diffusivities derived from membrane permeation studies (3.5 × 10^–15 m² s^–1 at <i>T</i> = 298 K for fractional occupancy Θ ≈ 0.99) and sorption uptake (<i>D</i>_i,MS ≈ 10^–20 m² s^–1 at 323 K) are several orders of magnitude larger or smaller than the microscopic self-diffusion coefficient <i>D</i>⁰_self, which was derived from relaxation time analysis. This experimental finding is attributed to the limits of macroscopic measurements

Plasmonic Semiconductor Nanoparticles in a Metal–Organic Framework Structure and Their <i>in Situ</i> Cation Exchange

Composites of nanoparticles (NPs) in metal–organic frameworks (MOFs) combine the versatile properties of NPs with the defined porosity of MOFs. Here, we show the encapsulation of plasmonic semiconductor NPs in ZIF-8 crystals. Both p-type and n-type doped plasmonic semiconductor NPs (consisting of Cu_2–<i>x</i>Se and indium tin oxide, respectively) are encapsulated. The plasmonic and structural properties of each system are preserved during the formation of the composites. Furthermore, we demonstrate the accessibility of the NPs integrated in ZIF-8 via the successful first-time <i>in situ</i> cation exchange of MOF-embedded Cu_2–<i>x</i>Se NPs to HgSe NPs and Ag₂Se NPs. This ion exchange occurs without influencing the composition or structural integrity of the metal–organic framework. This approach hence allows a fixation of plasmonic nanoparticles avoiding strong plasmon–plasmon coupling but still keeping the plasmonic nanoparticles accessible