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Charge transport in two zinc metal-organic frameworks (MOFs) has been investigated using periodic semiempirical molecular orbital calculations with the AM1* Hamiltonian. Restricted Hartree-Fock calculations underestimate the band gap using Koopmans theorem (ca. 2 eV compared to the experimental value of 2.8 eV). However, it almost doubles when the constraint on the wave function to remain spin-restricted is removed and the energies of the UHF Natural Orbitals are used. Charge-transport simulations using propagation of the electron- or hole-density in imaginary time allow charge-transport paths and mechanisms to be determined. The calculated relative mobilities in the directions of the three crystal axes agree with experimental expectations, but the absolute values are not reliable using the current technique. Hole-mobility along the crystal c -axis (along the metal stacks) is found to be 13 times higher in the zinc MOF with anthracene linker (Zn-ANMOF-74) than in the other directions, whereas the factor is far smaller (1.7) for electron mobility. Directional preferences are far less distinct in the equivalent structure with phenyl linkers (Zn-MOF-74). The imaginary-time simulation technique does not give quantitative mobilities. The simulations reveal a change in mechanism between the different directions: Coherent polaron migration is observed along the stacks but tunneling hops between them.

We report the synthesis of a unique cubic metal–organic framework (MOF), Fe‐HHTP‐MOF, comprising hexahydroxytriphenylene (HHTP) supertetrahedral units and FeIII ions, arranged in a diamond topology. The MOF is synthesized under solvothermal conditions, yielding a highly crystalline, deep black powder, with crystallites of 300–500 nm size and tetrahedral morphology. Nitrogen sorption analysis indicates a highly porous material with a surface area exceeding 1400 m2 g−1. Furthermore, Fe‐HHTP‐MOF shows broadband absorption from 475 up to 1900 nm with excellent absorption capability of 98.5 % of the incoming light over the visible spectral region. Electrical conductivity measurements of pressed pellets reveal a high intrinsic electrical conductivity of up to 10−3 S cm−1. Quantum mechanical calculations predict Fe‐HHTP‐MOF to be an efficient electron conductor, exhibiting continuous charge‐carrier pathways throughout the structure. [ABSTRACT FROM AUTHOR]

The rising demand for clean water for a growing and increasingly urban global population is one of the most urgent issues of our time. Here, we introduce the synthesis of a unique nanoscale architecture of pillar‐like Co‐CAT‐1 metal–organic framework (MOF) crystallites on gold‐coated woven stainless steel meshes with large, 50 μm apertures. These nanostructured mesh surfaces feature superhydrophilic and underwater superoleophobic wetting properties, allowing for gravity‐driven, highly efficient oil–water separation featuring water fluxes of up to nearly one million L m−2 h−1. Water physisorption experiments reveal the hydrophilic nature of Co‐CAT‐1 with a total water vapor uptake at room temperature of 470 cm3 g−1. Semiempirical molecular orbital calculations shed light on water affinity of the inner and outer pore surfaces. The MOF‐based membranes enable high separation efficiencies for a number of liquids tested, including the notorious water pollutant, crude oil, affording chemical oxygen demand (COD) concentrations below 25 mg L−1 of the effluent. Our results demonstrate the great impact of suitable nanoscale surface architectures as a means of encoding on‐surface extreme wetting properties, yielding energy‐efficient water‐selective large‐aperture membranes. [ABSTRACT FROM AUTHOR]

Crystalline and porous framework materials with appreciable charge carrier mobility hold promise as a new semiconducting platform. Through the concepts of reticular chemistry, numerous two‐ and three‐dimensional crystalline and porous frameworks with encoded properties enabling significant electrical conductivity are in reach. Prominent members of this group are the metal‐organic frameworks (MOFs), which recently created scientific excitement as highly conductive materials. Herein, we discuss the recent prominent examples reported for electrically conducting MOFs with regards to their synthesis, structural and electronic properties and possible applications. We frame our discussion according to structural features of the MOFs, covering both layered 2D and 3D frameworks. [ABSTRACT FROM AUTHOR]

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Biomass-derived lactic acid (LA) is an important platform chemical towards the sustainable production of numerous materials. However, the fermentation process currently in use is limited by the difficult recovery of the LA product from the fermentation broth and results in the generation of stoichiometric amounts of gypsum waste. Herein, we show that metal-organic frameworks (MOFs) of the UiO-66(Zr) type are effective adsorbents for the separation of LA from aqueous (buffer) solutions. These frameworks based on zirconium clusters and terephthalic acid derivatives display a tremendous uptake (up to 42 wt %) and a high affinity for LA. The latter can further be tuned by changing the hydrogen-bonding properties of the functional groups present on the organic ligand. A Rietveld refinement disclosed the specific interaction of LA with the clusters of UiO-66(Zr) and a preferential adsorption on open zirconium sites. Taking advantage of the catalytic activity of UiO-66(Zr), desorption of LA was performed in alcohols to recover up to 73 % as ester. Applied to the recovery of LA, adsorption and reactive desorption offer a direct and gypsum-free strategy as an alternative for the current multi-step process. [ABSTRACT FROM AUTHOR]

Keywords: electrical conductivity; iron-catecholate; metal-organic frameworks; porosity; three-dimensional framework EN electrical conductivity iron-catecholate metal-organic frameworks porosity three-dimensional framework 17893 17893 1 08/05/21 20210809 NES 210809 B Fe-HHTP-MOF b , ein einzigartiges kubisches metallorganisches Gerüst (MOF), das aus supertetraedrischen Hexahydroxytriphenylen(HHTP)-Einheiten und in Rautentopologie angeordneten Fe SP III sp -Ionen aufgebaut ist, wird im Forschungsartikel auf S. 18213 von Thomas Bein, Dana D. Medina et al. vorgestellt. GLO:OL3/09aug21:ange202106478-toc-0001.jpg PHOTO (COLOR): . gl GLO:OL3/09aug21:ange202106478-toc-0001.jpg PHOTO (COLOR): . gl B Fe-HHTP-MOF b , ein einzigartiges kubisches metallorganisches Gerüst (MOF), das aus supertetraedrischen Hexahydroxytriphenylen(HHTP)-Einheiten und in Rautentopologie angeordneten Fe SP III sp -Ionen aufgebaut ist, wird im Forschungsartikel auf S. 18213 von Thomas Bein, Dana D. Medina et al. vorgestellt. Fe-HHTP-MOF ist ein hochkristallines, poröses und tiefschwarzes Material, das eine hohe elektrische Leitfähigkeit aufweist. [Extracted from the article]

Fe-HHTP-MOF is a highly crystalline, porous, and deep black material featuring high electrical conductivity. Keywords: electrical conductivity; iron-catecholate; metal-organic frameworks; porosity; three-dimensional framework EN electrical conductivity iron-catecholate metal-organic frameworks porosity three-dimensional framework 17749 17749 1 08/05/21 20210809 NES 210809 B Fe-HHTP-MOF b , a unique cubic metal-organic framework (MOF) comprising hexahydroxytriphenylene (HHTP) supertetrahedral units and Fe SP III sp ions arranged in a diamond topology, is reported by Thomas Bein, Dana D. Medina et al. in their Research Article on page 18065. Fe-HHTP-MOF is a highly crystalline, porous, and deep black material featuring high electrical conductivity. [Extracted from the article]

Controlled on-surface film growth of porous and crystalline frameworks is a central prerequisite for incorporating these materials into functional platforms and operational devices. Here, we present the synthesis of thin zirconium-based metal-organic framework (MOF) films by vapor-assisted conversion (VAC). We established protocols adequate for the growth of UiO-66, UiO-66(NH2), UiO-67, and UiO-68(NH2) as well as the porous interpenetrated Zr-organic framework, PPPP-PIZOF-1, as highly oriented thin films. Through the VAC approach, precursors in a cast solution layer on a bare gold surface are reacting to form a porous continuous MOF film, oriented along the [111] crystal axis, by exposure to a solvent vapor at elevated temperature of 100 °C and 3 h reaction time. It was found that the concentration of dicarboxylic acid, the modulator, the droplet volume, and the reaction time are vital parameters to be controlled for obtaining oriented MOF films. Using VAC for the MOF film growth on gold surfaces modified with thiol SAMs and on a bare silicon surface yielded oriented MOF films, rendering the VAC process robust toward chemical surface variations. Ethanol sorption experiments show that a substantial part of the material pores is accessible. Thereby, the practical VAC method is an important addition to the toolbox of synthesis methods for thin MOF films. We expect that the VAC approach will open new horizons in the formation of highly defined functional thin MOF films for numerous applications. [ABSTRACT FROM AUTHOR]