Browsing by Author "Turner, DR"
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- ItemAnisotropic thermal and guest-induced responses of an ultramicroporous framework with rigid linkers(John Wiley & Sons, Inc, 2018-02-16) Auckett, JE; Duyker, SG; Izgorodina, EI; Hawes, CS; Turner, DR; Batten, SR; Peterson, VKThe interdependent effects of temperature and guest uptake on the structure of the ultramicroporous metal–organic framework [Cu3(cdm)4] (cdm=C(CN)2(CONH2)−) were explored in detail by using in situ neutron scattering and density functional theory calculations. The tetragonal lattice displays an anisotropic thermal response related to a hinged “lattice-fence” mechanism, unusual for this topology, which is facilitated by pivoting of the rigid cdm anion about the Cu nodes. Calculated pore-size metrics clearly illustrate the potential for temperature-mediated adsorption in ultramicroporous frameworks due to thermal fluctuations of the pore diameter near the value of the target guest kinetic diameter, though in [Cu3(cdm)4] this is counteracted by a competing contraction of the pore with increasing temperature as a result of the anisotropic lattice response. © 2018 Wiley-VCH Verlag GmbH & Co.
- ItemAtomic-scale explorations of stimulus-responsive framework properties in an ultramicroporous gas sorbent(Society of Crystallographers in Australia and New Zealand, 2017-12-03) Auckett, JE; Duyker, SG; Izgorodina, EI; Hawes, CS; Turner, DR; Batten, SS; Peterson, VKFunctional microporous materials capable of efficiently separating and/or storing gases at noncryogenic temperatures are sought for a wide variety of important industrial applications, including pre- and post-combustion carbon capture, hydrogen fuel storage, and the purification of component gases from air. Understanding the atomic-scale interactions between the host material and guest species under variable operating conditions is essential for obtaining information about adsorption and separation mechanisms, which can in turn be used to design better sorbents targeted at specific applications. The ultramicroporous metal-organic framework [Cu3(cdm)4] (cdm = C(CN)2CONH2 -) was recently reported to exhibit moderately selective adsorption of CO2 over CH4, along with excellent exclusion of elemental gases such as H2 and N2 [1]. Although the very small pore diameter (3–4 Å) results in unpromisingly slow diffusion dynamics, its close similarity to the kinetic diameters of many small gas molecules [2] also raises the prospect of altering the gas sorption and selectivity characteristics of the material via minor structural modifications, such as might be introduced by changing the temperature and/or guest concentration during sorbent operation under industrially relevant conditions. Using a combination of in situ neutron scattering experiments and density functional theory-based calculations, we examine in detail the interplay between lattice shape, pore size, temperature, and CO2 concentration in [Cu3(cdm)4]. The rare and interesting fundamental property of areal negative thermal expansion (NTE) in [Cu3(cdm)4] is attributed to a new variation of a well-known NTE mechanism, and is triggered by dynamic motions of the rigid cdm ligand within the constraints of the complicated framework topology. Although the thermal response of the pore diameter is surprisingly insignificant due to competition between multiple effects, the potential for similar materials to exhibit temperature induced changes in adsorption properties is clearly demonstrated. This study illustrates the breadth and depth of information that can be obtained by combining the power of experimental and theoretical characterisation in an approach that is generally applicable to crystalline sorbent systems.
- ItemHydrogen Bonding of O-Ethylxanthate Compounds and Neutron Structural Determination of C–H···S Interactions(CSIRO Publishing, 2014-10-10) Macreadie, LK; Edwards, AJ; Chesman, ASR; Turner, DRA range of ethylxanthate (EtXn) salts, containing either protic or aprotic cations (guanidinium (1), methylammonium (2), dimethylammonium (3), trimethylammonium (4), tetramethylammonium (5), tetraethylammonium (6), and tetrapropylammonium (7)), have been synthesised and structurally characterised. The cations in these compounds differ in their degree of hydrogen-bonding ability, i.e. the number of donor groups, with significant structural consequences. Compounds 1–4 contain cations that are able to form N–H···S hydrogen bonds, with six, three, two, and one donor groups in 1–4 respectively. The number of donor atoms affects greatly the dimensionality of the hydrogen-bonding networks in the solid state. The structure of 1 has a 3-D hydrogen-bonding network, 2 and 3 form 2-D sheets and 1-D chains respectively, whereas the lone NH donor group in 4 has strong hydrogen bonding only within a discrete cation–anion pair. The tetraalkylammonium salts 5–7 have no strong hydrogen bonding, with only C–H···S and C–H···O interactions possible. To determine unambiguously the presence of such interactions, single-crystal Laue neutron diffraction data were obtained for compound 5, providing a fully anisotropic model, which can be used to rationalise potential close interactions in the other structures. The neutron structure of 5 confirms the existence of C–H···S hydrogen bonds, with the H···S distance falling well within the sum of the van der Waals radii of the atoms. The close-packing in 5–7 is mediated solely through these weak interactions, with the size of the cations influencing the structures. © CSIRO 1996-2020
- ItemInsights into selective gas sorbent functionality gained by using time-resolved neutron diffraction(John Wiley & Sons, Inc, 2018-05-05) Auckett, JE; Duyker, SG; Turner, DR; Batten, SR; Peterson, VKAn understanding of the atomic-scale interactions between gas sorbent materials and their molecular guests is essential for the identification of the origins of desirable function and the rational optimization of performance. However, characterizations performed on equilibrated sorbent–guest systems may not accurately represent their behavior under dynamic operating conditions. The emergence of fast (minute-scale) neutron powder diffraction coupled with direct, real-time quantification of gas uptake opens up new possibilities for obtaining knowledge about concentration-dependent effects of guest loading upon function-critical features of sorbent materials, including atomic structure, diffusion pathways, and thermal expansion of the sorbent framework. This article presents a detailed investigation of the ultramicroporous metal–organic framework [Cu3(cdm)4] as a case study to demonstrate the variety of insights into sorbent performance that can be obtained from real-time characterizations using neutron diffraction. © 2018 Wiley-VCH Verlag GmbH & Co
- ItemInvestigation of steric influences on hydrogen-bonding motifs in cyclic rreas by using x-ray, neutron, and computational methods(Wiley-V C H Verlag GMBH, 2013-11-01) McCormick, LJ; McDonnell-Worth, C; Platts, JA; Edwards, AJ; Turner, DRA series of urea-derived heterocycles, 5N-substituted hexahydro-1,3,5-triazin-2-ones, has been prepared and their structures have been determined for the first time. This family of compounds only differ in their substituent at the 5-position (which is derived from the corresponding primary amine), that is, methyl (1), ethyl (2), isopropyl (3), tert-butyl (4), benzyl (5), N,N-(diethyl)ethylamine (6), and 2-hydroxyethyl (7). The common heterocyclic core of these molecules is a cyclic urea, which has the potential to form a hydrogen-bonding tape motif that consists of self-associative R-2(2)(8) dimers. The results from X-ray crystallography and, where possible, Laue neutron crystallography show that the hydrogen-bonding motifs that are observed and the planarity of the hydrogen bonds appear to depend on the steric hindrance at the -carbon atom of the Nsubstituent. With the less-hindered substituents, methyl and ethyl, the anticipated tape motif is observed. When additional methyl groups are added onto the -carbon atom, as in the isopropyl and tert-butyl derivatives, a different 2D hydrogen-bonding motif is observed. Despite the bulkiness of the substituents, the benzyl and N,N-(diethyl)ethylamine derivatives have methylene units at the -carbon atom and, therefore, display the tape motif. The introduction of a competing hydrogen-bond donor/acceptor in the 2-hydroxyethyl derivative disrupts the tape motif, with a hydroxy group interrupting the NHOC interactions. The geometry around the hydrogen-bearing nitrogen atoms, whether planar or non-planar, has been confirmed for compounds 2 and 5 by using Laue neutron diffraction and rationalized by using computational methods, thus demonstrating that distortion of O-C-N-H torsion angles occurs to maintain almost-linear hydrogen-bonding interactions. © 2014, Wiley-VCH Verlag GmbH & Co. KGaA
- ItemNeutron diffraction and in situ gas-loading investigations of functional MOFs for energy-relevant gas separations(Australian Institute of Nuclear Science and Engineering (AINSE), 2012-11-08) Duyker, SG; Peterson, VK; Ogilvie, SH; Turner, DR; Hill, MR; D'Alessandro, DM; Kepert, CJIntense research is currently directed towards realising metal-organic frameworks (MOFs) for industrially-applied gas separation and storage due to their unique structural properties, including: robustness; thermal and chemical stability; unprecedented internal surface area; and high void volume. A particular focus of current research is the development of MOFs for the separation of CO, from the other components of flue gas in fossil-fuelled power plants. The use of NPD to study gas adsorption in framework materials is a relatively new but growing field. Structural measurements, which show the arrangement of both the host and guest, allow derivation of the nature of the host-guest interaction, and the host's response to the guest. The capability to perform these measurements, with accurate gas dosing and temperature control, has recently been realised at ANSTO's Bragg Institute. Using these techniques, we have investigated the adsorption mechanisms of a number of gases in selected new and established MOFs that display impressive selectivity for specific gases. The location and orientation of industrially-relevant gases including D2, 02, CO2, and CD4, within their crystal structures provide insights into the modes of binding, which will help to tune the materials' performance and benefit the design and development process for the next generation of materials.
- ItemA neutron diffraction study of hydrogen bonding in isostructural potassium and ammonium lanthanoidates(Royal Society of Chemistry, 2014-10-08) Emerson, AJ; Edwards, AJ; Batten, SR; Turner, DRTwo isostructural series of compounds NH4[Ln(cdm)4(H2O)4]·18c6·3H2O (1Ln) and [K(18c6)(H2O)2][Ln(cdm)4(H2O)4]·H2O (2Ln) have been synthesised and structurally characterised (Ln = Gd, Dy, Er, cdm = C(CN)2(CONH2)−). These two classes of compounds are shown to be essentially isostructural to each other despite the change in counter-cation (ammonium vs. potassium) and the ensuing changes in coordination and hydrogen-bonding of water molecules in the structure. Structural data for 1Dy and 2Dy have been obtained using single crystal Laue neutron diffraction, allowing the precise location of all hydrogen atoms to be determined using fully anisotropic models. Both 1 and 2 contain the anionic complex [Ln(cdm)4(H2O)4]− in which the 8-coordinate lanthanoid is coordinated by a ring of four O-bound cdm ligands supported by inter-ligand N–H⋯O hydrogen bonds. The structures pack with complicated hydrogen-bonding networks in which both coordinated and non-coordinated water molecules are hydrogen-bond donors and all of the nitrile groups of the cdm ligands are hydrogen-bond acceptors. The change in cation between ammonium and potassium affects two water molecule sites which are both coordinated in 2Ln but not in 1Ln; in 1Ln one of these water molecules forms a hydrogen bond with NH4+ whilst the other has neither a coordination interaction nor a hydrogen bond to its oxygen atom. © The Royal Society of Chemistry.
- ItemNitrile groups as hydrogen-bond acceptors in a donor-rich hydrogen-bonding network(Royal Society of Chemistry, 2012-01-01) Turner, DR; Edwards, AJ; Piltz, ROA complex hydrogen-bonding network involving the guanidinium cation and the dinitrile anion C(CN)(2)(CONH2)(-) has been studied using Laue neutron diffraction. The role of nitrile groups as hydrogen bond acceptors is highlighted in this donor-rich system combined with a survey of the CSD exploring R-2(1)(6) synthons containing nitrile groups. © 2012, Royal Society of Chemistry
- ItemUltramicroporous MOF with high concentration of vacant Cu 11 sites(American Chemical Society, 2015-07) McCormick, LJ; Duyker, SG; Thornton, AW; Hawes, CS; Hill, MR; Peterson, VK; Batten, SR; Turner, DRAn ultramicroporous metal–organic framework (MOF) is reported that contains 0.35 nm nanotube-like channels with an unprecedented concentration of vacant CuII coordination sites. The nonintersecting, narrow channels in [Cu3(cdm)4] (cdm = C(CN)2(CONH2)−) align in two perpendicular directions, structurally resembling copper-doped carbon nanotubes with CuII embedded in the walls of the channels. The combination of ultramicroporosity with the exposed CuII coordination sites gives size-based selectivity of CO2 over CH4, based on pore-size distribution and modeling. Neutron powder diffraction and molecular dynamics simulations show the close packing of single rows of guests within the tubular nanostructure and interaction of CO2 with the exposed metal sites. © 2014, American Chemical Society.