A series of nine Ce(iv)-based metal organic frameworks with the UiO-66 structure containing linker molecules of different sizes and functionalities were obtained under mild synthesis conditions and ...short reaction times. Thermal and chemical stabilities were determined and a Ce-UiO-66-BDC/TEMPO system was successfully employed for the aerobic oxidation of benzyl alcohol.
A new hydrothermally stable Al polycarboxylate metal–organic framework (MOF) based on a heteroatom bio‐derived aromatic spacer is designed through a template‐free green synthesis process. It appears ...that in some test conditions this MOF outperforms the heat reallocation performances of commercial SAPO‐34.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Metal-organic frameworks (MOFs) are microporous materials with huge potential for chemical processes. Structural collapse at high pressure, and transitions to liquid states at high temperature, have ...recently been observed in the zeolitic imidazolate framework (ZIF) family of MOFs. Here, we show that simultaneous high-pressure and high-temperature conditions result in complex behaviour in ZIF-62 and ZIF-4, with distinct high- and low-density amorphous phases occurring over different regions of the pressure-temperature phase diagram. In situ powder X-ray diffraction, Raman spectroscopy and optical microscopy reveal that the stability of the liquid MOF state expands substantially towards lower temperatures at intermediate, industrially achievable pressures and first-principles molecular dynamics show that softening of the framework coordination with pressure makes melting thermodynamically easier. Furthermore, the MOF glass formed by melt quenching the high-temperature liquid possesses permanent, accessible porosity. Our results thus imply a route to the synthesis of functional MOF glasses at low temperatures, avoiding decomposition on heating at ambient pressure.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Data Analysis WorkbeNch (DAWN) Basham, Mark; Filik, Jacob; Wharmby, Michael T. ...
Journal of synchrotron radiation,
20/May , Volume:
22, Issue:
3
Journal Article
Peer reviewed
Open access
Synchrotron light source facilities worldwide generate terabytes of data in numerous incompatible data formats from a wide range of experiment types. The Data Analysis WorkbeNch (DAWN) was developed ...to address the challenge of providing a single visualization and analysis platform for data from any synchrotron experiment (including single‐crystal and powder diffraction, tomography and spectroscopy), whilst also being sufficiently extensible for new specific use case analysis environments to be incorporated (e.g. ARPES, PEEM). In this work, the history and current state of DAWN are presented, with two case studies to demonstrate specific functionality. The first is an example of a data processing and reduction problem using the generic tools, whilst the second shows how these tools can be targeted to a specific scientific area.
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The porous metal‐organic framework (MOF) MIL‐160 Al(OH)(O2C‐C4H2O‐CO2) was investigated by means of high‐resolution powder X‐ray diffraction experiments using synchrotron radiation. The structures of ...the dehydrated, hydrated and nitrogen loaded forms of MIL‐160 are refined by the Rietveld method. The structure of the hydrated form, as postulated from solid state NMR and DFT calculations, is confirmed. The host–guest and thermal responses of this compound are also investigated. Adsorption of water is found to induce a phase transition from I41/amd (the dehydrated structure) to I41md (the hydrated structure), mediated by flexibility of the MOF framework. Water molecules were observed to arrange themselves with an ice‐like geometry. Conversely, adsorption of more weakly interacting N2 into the structure or thermal treatment (cooling the sample from 400 to 80 K) leads to no phase transition, indicating that the phase transition is induced by the strong interactions of H2O with the framework. The accuracy of the refined structures is investigated by DFT calculations, which show very small deviations in optimised atomic positions and lattice parameters.
The structure of Al‐MOF MIL‐160 Al{OH(O2C‐C4H2O‐CO2)}, postulated from solid state NMR and DFT calculations, is confirmed by Rietveld refinement of high‐resolution synchrotron powder X‐ray diffraction. Its H2O and N2 host–guest complexes were also refined & demonstrate structural flexibility. DFT calculations demonstrate the high‐accuracy of the refined structures.
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Stimuli-responsive flexible metal-organic frameworks (MOFs) remain at the forefront of porous materials research due to their enormous potential for various technological applications. Here, we ...introduce the concept of frustrated flexibility in MOFs, which arises from an incompatibility of intra-framework dispersion forces with the geometrical constraints of the inorganic building units. Controlled by appropriate linker functionalization with dispersion energy donating alkoxy groups, this approach results in a series of MOFs exhibiting a new type of guest- and temperature-responsive structural flexibility characterized by reversible loss and recovery of crystalline order under full retention of framework connectivity and topology. The stimuli-dependent phase change of the frustrated MOFs involves non-correlated deformations of their inorganic building unit, as probed by a combination of global and local structure techniques together with computer simulations. Frustrated flexibility may be a common phenomenon in MOF structures, which are commonly regarded as rigid, and thus may be of crucial importance for the performance of these materials in various applications.
A continuous flow reactor was developed for the synthesis of porous metal-organic frameworks (MOFs) under mild reaction conditions. Commodity hardware was used to assemble the device, giving it a ...great degree of flexibility in its configuration. The use of paraffin to encapsulate reactions and also ultrasonic treatment were employed to prevent clogging of the reactor. Reactor design was optimised through studies of the synthesis of zirconium carboxylate framework UiO-66. Synthesis of the aluminium carboxylate CAU-13 was also performed, to demonstrate the versatility of the device. Finally the reactor was used to synthesise a new cadmium phosphonate framework, bearing the STA-12 network.
While titanium‐based metal–organic frameworks (MOFs) have been widely studied for their (photo)catalytic potential, only a few TiIV MOFs have been reported owing to the high reactivity of the ...employed titanium precursors. The synthesis of COK‐47 is now presented, the first Ti carboxylate MOF based on sheets of TiIVO6 octahedra, which can be synthesized with a range of different linkers. COK‐47 can be synthesized as an inherently defective nanoparticulate material, rendering it a highly efficient catalyst for the oxidation of thiophenes. Its structure was determined by continuous rotation electron diffraction and studied in depth by X‐ray total scattering, EXAFS, and solid‐state NMR. Furthermore, its photoactivity was investigated by electron paramagnetic resonance and demonstrated by catalytic photodegradation of rhodamine 6G.
COK‐47, the first Ti carboxylate sheet‐based MOF, can be synthesized as pristine or inherently defective nanoparticulate material. Its structure was extensively characterized and its defects render it a highly efficient catalyst for the oxidation of thiophenes. The material also features photocatalytic activity.
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We investigate the pressure-dependent mechanical behaviour of the zeolitic imidazolate framework ZIF-4 (M(im)
; M
= Co
or Zn
, im
= imidazolate) with high pressure, synchrotron powder X-ray ...diffraction and mercury intrusion measurements. A displacive phase transition from a highly compressible open pore (
) phase with continuous porosity (space group
, bulk modulus ∼1.4 GPa) to a closed pore (
) phase with inaccessible porosity (space group
2
/
, bulk modulus ∼3.3-4.9 GPa) is triggered by the application of mechanical pressure. Over the course of the transitions, both ZIF-4 materials contract by about 20% in volume. However, the threshold pressure, the reversibility and the immediate repeatability of the phase transition depend on the metal cation. ZIF-4(Zn) undergoes the
phase transition at a hydrostatic mechanical pressure of only 28 MPa, while ZIF-4(Co) requires about 50 MPa to initiate the transition. Interestingly, ZIF-4(Co) fully returns to the
phase after decompression, whereas ZIF-4(Zn) remains in the
phase after pressure release and requires subsequent heating to switch back to the
phase. These variations in high pressure behaviour can be rationalised on the basis of the different electron configurations of the respective M
ions (3d
for Zn
and 3d
for Co
). Our results present the first examples of
phase transitions (
breathing transitions) of ZIFs driven by mechanical pressure and suggest potential applications of these functional materials as shock absorbers, nanodampers, or in mechanocalorics.
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