Freshly ground: Improved mechanochemical methodologies, such as liquid-assisted grinding and ion- and liquid-assisted grinding enable the rapid and topologically selective synthesis of porous and nonporous zeolitic imidazolate frameworks with diverse topologies, at room temperature and directly from zinc oxide

A fast method for crystal structure determination using crystal structure prediction and solid-state (1)H NMR is presented. This technique does not need any prior knowledge except the chemical formula; resonance assignment is not necessary. Starting from an ensemble of predicted crystal structures for powdered thymol, comparison between experimental and calculated (1)H solid-state isotropic NMR chemical shifts is sufficient to determine which predicted structure corresponds to the powder under study. The same approach using proton-proton spin-diffusion data is successful and can be used for cross-validation.

A protocol for the ab initio crystal structure determination of powdered solids at natural isotopic abundance by combining solid-state NMR spectroscopy, crystal structure prediction, and DFT chemical shift calculations was evaluated to determine the crystal structures of four small drug molecules: cocaine, flutamide, flufenamic acid, and theophylline. For cocaine, flutamide and flufenamic acid, we find that the assigned 1 H isotropic chemical shifts provide sufficient discrimination to determine the correct structures from a set of predicted structures using the root-mean-square deviation (rmsd) between experimentally determined and calculated chemical shifts. In most cases unassigned shifts could not be used to determine the structures. This method requires no prior knowledge of the crystal structure, and was used to determine the correct crystal structure to within an atomic rmsd of less than 0.12 Å with respect to the known reference structure. For theophylline, the NMR spectra are too simple to allow for unambiguous structure selection.

A protocol for the structure determination of powdered solids at natural abundance by NMR is presented and illustrated for the case of the small drug molecule thymol. The procedure uses proton spin-diffusion data from two-dimensional NMR experiments in combination with periodic DFT refinements incorporating (1)H and (13)C NMR chemical shifts. For thymol, the method yields a crystal structure for the powdered sample, which differs by an atomic root-mean-square-deviation (all atoms except methyl group protons) of only 0.07 A from the single crystal X-ray diffraction structure with DFT-optimized proton positions.

We describe a conceptually novel ''accelerated aging'' approach for the synthesis of metal-organic materials. This approach, inspired by natural mineral weathering processes, enables the synthesis of metal-organic structures from simple and inexpensive solid reactants upon exposure to catalytic amounts of an ammonium salt under conditions of high humidity and mild temperatures (up to 45 C). Accelerated aging exploits the inherent mobility of molecules and is entirely different from solutionbased (precipitation, solvothermal synthesis) or other solvent-free (mechanochemical synthesis) approaches to metal-organic materials that require either bulk solvent and/or thermo-or mechanochemical intervention. The present proof-of-principle study of accelerated aging demonstrates the catalysed and topologically specific transformation of ZnO into unusual close-packed varieties of zeolitic imidazolate frameworks (ZIFs) in a static, non-agitated reaction mixture. The reactivity is readily scaled up, as demonstrated by performing selected syntheses of quartz-and diamondoidtopology close-packed ZIFs in ten gram amounts. The latter framework, previously obtained only by using a large excess of reagents under hydrothermal conditions, is transformed into the well-known open framework ZIF-8 by exposure to methanol vapours at room temperature, suggesting an alternative to both solvothermal and mechanochemical approaches to these materials. A tentative proton-transfer mechanism underpinning the catalytic effect in accelerated aging is proposed, involving protonated imidazole as an intermediate.

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The black crystalline (aza)­triangulene-based covalent organic framework TANG-COF was synthesized from its trinitro-TANG precursor via a one-pot, two-step reaction involving Pd-catalyzed hydrogenation and polycondensation with an aromatic dialdehyde. High crystallinity and permanent porosity of the layered two-dimensional (2D) structure were established. The rigid, electron-rich trioxaazatriangulene (TANG) building block enables strong π-electron interactions manifested in broad absorptions across the visible and NIR regions (E g ≈ 1.2 eV). The high HOMO energy of TANG-COF (−4.8 eV) enables facile p doping, resulting in electrical conductivity of up to 10–2 S/cm and room-temperature paramagnetic behavior with a spin concentration of ∼10%. DFT calculations reveal dispersion of the highest occupied band both within the 2D polymer layers (0.28 eV) and along their π-stacked direction (0.95 eV).

Just a pinch of salt: Small amounts of salts accelerate and direct the mechanochemical construction of metal–organic frameworks (MOFs) from a metal oxide (see scheme; ILAG= ion‐ and liquid‐assisted grinding). The resulting rapid and room‐temperature synthesis demonstrates the ability to control mechanosynthesis of metal–organic compounds by templating, as well as the ability to use mechanochemistry to include ionic guests within neutral MOFs.