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21 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2, 3 [Next/Last]

Instruments / Technical Area	Publication Details	Published
I15-1-X-ray Pair Distribution Function (XPDF)	Entropy driven disorder–order transition of a metal–organic framework with frustrated flexibility Roman Pallach , Jan-Benedikt Weiss , Katrin Vollmari , Sebastian Henke Apl Materials 11 DOI: 10.1063/5.0144718 Diamond Proposal Number(s): [15895] Open Access Show Abstract ▼ Abstract: Flexible metal–organic frameworks (MOFs), showing a reversible phase change behavior in response to guest adsorption or temperature, provide unique opportunities for molecular separation or energy storage applications. Herein, we investigate the complex guest- and temperature-responsive behavior of a functionalized MOF-5 derivative. The material is characterized by a geometrically rigid network structure that is decorated with dispersion energy donating hexyloxy substituents. Distinguished by the phenomenon of frustrated flexibility, the functionalized MOF-5 derivative switches between a highly crystalline, cubic structure and a semi-crystalline, aperiodically distorted structure depending on guest adsorption and temperature. Via a combination of several variable temperature global and local structure techniques (x-ray diffraction, x-ray total scattering, and Fourier-transform IR spectroscopy), detailed insights into the complementary disorder–order transitions of the framework backbone and the dangling hexyloxy substituents are provided. Our results set the stage for the discovery of new responsive MOFs exhibiting a more complex phase change behavior interfacing periodic and aperiodic structural changes.	Apr 2023
I15-1-X-ray Pair Distribution Function (XPDF)	Modulating liquid–liquid transitions and glass formation in zeolitic imidazolate frameworks by decoration with electron-withdrawing cyano groups Jianbo Song , Louis Frentzel-Beyme , Roman Pallach , Pascal Kolodzeiski , Athanasios Koutsianos , Wen-Long Xue , Rochus Schmid , Sebastian Henke Journal Of The American Chemical Society 24 DOI: 10.1021/jacs.3c01933 Diamond Proposal Number(s): [21604] Show Abstract ▼ Abstract: The liquid phase of metal–organic frameworks (MOFs) is key for the preparation of melt-quenched bulk glasses as well as the shaping of these materials for various applications; however, only very few MOFs can be melted and transformed into stable glasses. Here, the solvothermal and mechanochemical preparation of a new series of functionalized derivatives of ZIF-4 (Zn(im)2, where im– = imidazolate and ZIF = zeolitic imidazolate framework) containing the cyano-functionalized imidazolate linkers CNim– (4-cynanoimidazolate) and dCNim– (4,5-dicyanoimidazolate) is reported. The strongly electron-withdrawing nature of the CN groups facilitates low-temperature melting of the materials (below 310 °C for some derivatives) and the formation of microporous ZIF glasses with remarkably low glass-transition temperatures (down to only about 250 °C) and strong resistance against recrystallization. Besides conventional ZIF-4, the CN-functionalized ZIFs are so far the only MOFs to show an exothermic framework collapse to a low-density liquid phase and a subsequent transition to a high-density liquid phase. By systematic adjustment of the fraction of cyano-functionalized linkers in the ZIFs, we derive fundamental insights into the thermodynamics of the unique polyamorphic nature of these glass formers as well as further design rules for the porosity of the ZIF glasses and the viscosity of their corresponding liquids. The results provide new insights into the unusual phenomenon of liquid–liquid transitions as well as a guide for the chemical diversification of meltable MOFs, likely with implications beyond the archetypal ZIF glass formers.	Apr 2023
I15-1-X-ray Pair Distribution Function (XPDF)	Quantification of gas-accessible microporosity in metal-organic framework glasses Louis Frentzel-Beyme , Pascal Kolodzeiski , Jan-Benedikt Weiß , Andreas Schneemann , Sebastian Henke Nature Communications 13 DOI: 10.1038/s41467-022-35372-5 Diamond Proposal Number(s): [21604] Open Access Show Abstract ▼ Abstract: Metal-organic framework (MOF) glasses are a new class of glass materials with immense potential for applications ranging from gas separation to optics and solid electrolytes. Due to the inherent difficulty to determine the atomistic structure of amorphous glasses, the intrinsic structural porosity of MOF glasses is only poorly understood. Here, we investigate the porosity features (pore size and pore limiting diameter) of a series of prototypical MOF glass formers from the family of zeolitic imidazolate frameworks (ZIFs) and their corresponding glasses. CO2 sorption at 195 K allows quantifying the microporosity of these materials in their crystalline and glassy states, also providing excess to the micropore volume and the apparent density of the ZIF glasses. Additional hydrocarbon sorption data together with X-ray total scattering experiments prove that the porosity features of the ZIF glasses depend on the types of organic linkers. This allows formulating design principles for a targeted tuning of the intrinsic microporosity of MOF glasses. These principles are counterintuitive and contrary to those established for crystalline MOFs but show similarities to strategies previously developed for porous polymers.	Dec 2022
I15-Extreme Conditions	Tuning the high-pressure phase behaviour of highly compressible zeolitic imidazolate frameworks: from discontinuous to continuous pore closure by linker substitution Jianbo Song , Roman Pallach , Louis Frentzel-Beyme , Pascal Kolodzeiski , Gregor Kieslich , Pia Vervoorts , Claire L. Hobday , Sebastian Henke Angewandte Chemie International Edition DOI: 10.1002/anie.202117565 Diamond Proposal Number(s): [21603] Open Access Show Abstract ▼ Abstract: The high-pressure behaviour of flexible zeolitic imidazolate frameworks (ZIFs) of the ZIF-62 family with the chemical composition M(im)2-x(bim)x is presented (M2+ = Zn2+, Co2+; im– = imidazolate; bim– = benzimidazolate, 0.02 ≤ x ≤ 0.37). High-pressure powder X-ray diffraction shows that the materials contract reversibly from an open pore (op) to a closed pore (cp) phase under a hydrostatic pressure of up to 4000 bar. Sequentially increasing the bim– fraction (x) reinforces the framework, leading to an increased threshold pressure for the op-to-cp phase transition, while the total volume contraction across the transition decreases. Most importantly, the typical discontinuous op-to-cp transition (first order) changes to an unusual continuous transition (second order) for x ≥ 0.35. This allows finetuning the void volume and the pore size of the material continuously by adjusting the pressure, thus opening new possibilities for MOFs in pressure-switchable devices, membranes, and actuators.	Feb 2022
I19-Small Molecule Single Crystal Diffraction	Guest-mediated phase transitions in a flexible pillared-layered metal-organic framework under high-pressure Gemma F. Turner , Scott C. Mckellar , David Robert Allan , Anthony K. Cheetham , Sebastian Henke , Stephen A. Moggach Chemical Science DOI: 10.1039/D1SC03108B Open Access Show Abstract ▼ Abstract: The guest-dependent flexibility of the pillared-layered metal-organic framework (MOF), Zn2bdc2dabco·X(guest), where guest = EtOH, DMF or benzene, has been examined by high-pressure single crystal X-ray diffraction. A pressure-induced structural phase transition is found for the EtOH- and DMF-included frameworks during compression in a hydrostatic medium of the guest species, which is dependent upon the nature and quantity of the guest in the channels. The EtOH-included material undergoes a phase transition from P4/mmm to C2/m at 0.69 GPa, which is accompanied by a change in the pore shape from square to rhombus via super-filling of the pores. The DMF-included material undergoes a guest-medaited phase transition from I4/mcm to P4/mmm at 0.32 GPa via disordering of the DMF guest. In contrast, the benzene-included framework features a structure with rhombus-shaped channels at ambient pressure and shows direct compression as well as negative linear compressibility parallel to the long diagonal of the channels under hydrostatic pressure. These results demonstrate the large influence of guest molecules on the phase behavior of flexible MOFs. Thus, guest-mediated framework flexibility is useful to engineering MOFs with bespoke pore shapes and compressibility.	Sep 2021
I15-1-X-ray Pair Distribution Function (XPDF)	Frustrated flexibility in metal-organic frameworks Roman Pallach , Julian Keupp , Kai Terlinden , Louis Frentzel-Beyme , Marvin Kloß , Andrea Machalica , Julia Kotschy , Suresh K. Vasa , Philip A. Chater , Christian Sternemann , Michael T. Wharmby , Rasmus Linser , Rochus Schmid , Sebastian Henke Nature Communications 12 DOI: 10.1038/s41467-021-24188-4 Diamond Proposal Number(s): [15895, 21262, 21604] Open Access Show Abstract ▼ Abstract: 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.	Jul 2021
I15-1-X-ray Pair Distribution Function (XPDF)	Meltable mixed-linker zeolitic imidazolate frameworks and their microporous glasses - from melting point engineering to selective hydrocarbon sorption Louis Frentzel-Beyme , Marvin Kloss , Pascal Kolodzeiski , Roman Pallach , Sebastian Henke Journal Of The American Chemical Society DOI: 10.1021/jacs.9b05558 Diamond Proposal Number(s): [21474, 23134] Show Abstract ▼ Abstract: Porous glasses from metal-organic frameworks (MOFs) represent a new class of functional inorganic-organic glasses, which have been proposed for applications ranging from solid electrolytes to radioactive waste storage. So far, just a few zeolitic imidazolate frameworks (ZIFs), a subset of MOFs, have been reported to melt and the structural and compositional requirements for MOF melting and glass formation are poorly understood. Here, we show how the melting point of the prototypical ZIF-4/ZIF-62(M) frameworks (composition M(im)2–x(bim)x; M2+ = Co2+, Zn2+; im– = imidazolate; bim– = benzimidazolate) can be controlled systematically by adjusting the molar ratio of the two imidazolate-type linkers im– and bim–. By covering the entire range from x = 0 to x = 0.35, we unveil a delicate transition from ZIF materials showing sequential amorphization/recrystallization to derivatives exhibiting coherent melting and a liquid phase that is stable over a large temperature window. The melting point of this ZIF system is a direct function of x and can be lowered from ca. 430 °C to only 370 °C – by far the lowest melting point reported for a three-dimensional porous MOF. On the basis of our results, we postulate compositional requirements for ZIF melting and glass formation, which may guide the search for other meltable ZIFs. Moreover, gas physisorption experiments establish that the ZIF glasses adsorb technologically relevant C3 and C4 hydrocarbons. Importantly, the adsorption kinetics are much faster for propylene compared to propane and are also dependent on the im–:bim– ratio, thus demonstrating the potential of these ZIF glasses for applications in gas separation.	Jul 2019
I15-Extreme Conditions	Flexibility control in alkyl ether-functionalized pillared-layered MOFs by a Cu/Zn mixed metal approach Andreas Schneemann , Robin Rudolf , Samuel J. Baxter , Pia Vervoorts , Inke Hante , Kira Khaletskaya , Sebastian Henke , Gregor Kieslich , Roland A. Fischer Dalton Transactions DOI: 10.1039/C9DT01105F Diamond Proposal Number(s): [13560] Show Abstract ▼ Abstract: Flexible metal-organic frameworks (MOFs) exhibit large potential as next-generation materials in areas such as gas sensing, gas separation and mechanical damping. By using a mixed metal approach, we report how the stimuli reponsive phase transition of flexible pillared-layered MOFs can be tuned over a wide range. Different Cu2+ to Zn2+ metal ratios are incorporated into the materials by using a simple solvothermal approach. The properties of the obtained materials are probed by differential scanning calorimetry and CO2 sorption measurements, revealing stimuli responsive behaviour as a function of metal ratio. Pair distribution functions derived from X-ray total scattering experiments suggest a distortion of the M2 paddlewheel as a function of the Cu content. We rationalize these phenomena by the different distortion energies of Cu2+ and Zn2+ ions to deviate from the square pyramidal structure of the relaxed paddlewheel node.Our work follows on from the large interest in tuning and understanding the materials properties of flexible MOFs, highlighting the large number of parameters that can be used for the targeted manipulation and design of properties of these fascinating materials.	Apr 2019
I15-1-X-ray Pair Distribution Function (XPDF)	Porous purple glass – a cobalt imidazolate glass with accessible porosity from a meltable cobalt imidazolate framework Louis Frentzel-Beyme , Marvin Kloß , Roman Pallach , Soma Salamon , Henning Moldenhauer , Joachim Landers , Heiko Wende , Jörg Debus , Sebastian Henke Journal Of Materials Chemistry A 7, 985 - 990 DOI: 10.1039/C8TA08016J Diamond Proposal Number(s): [21474] Show Abstract ▼ Abstract: We report the first microporous cobalt imidazolate glass obtained from a meltable cobalt-based zeolitic imidazolate framework, ZIF-62(Co). Crystalline ZIF-62(Co) is constructed from Co2+ cations and two different imidazolate-type linkers, namely conventional imidazolate and benzimidazolate. The microporous framework melts at ∼430 °C and converts into a glass upon cooling to room temperature. X-Ray total scattering and Raman spectroscopy reveal that the local structure of the glass and the crystalline parent material are very similar. Magnetic measurements and X-ray diffraction uncover that ZIF-62(Co) partially decomposes upon melting and glass formation resulting in the reduction of ∼3% of the Co2+ ions to metallic cobalt. Most importantly, the ZIF glass retains almost 50% of the porosity of crystalline ZIF-62(Co). Our results pave the way for the realisation of metal–organic framework glasses containing open shell metal ions, as well as the application of these porous glasses in gas separation, energy storage and catalysis.	Jan 2019
I12-JEEP: Joint Engineering, Environmental and Processing	Control of metal-organic framework crystallization by metastable intermediate pre-equilibrium species Hamish Yeung , Adam F. Sapnik , Felicity Massingberd-Mundy , Michael W. Gaultois , Yue Wu , Duncan X. Fraser , Sebastian Henke , Roman Pallach , Niclas Heidenreich , Oxana Magdysyuk , Nghia T. Vo , Andrew L. Goodwin Angewandte Chemie International Edition DOI: 10.1002/anie.201810039 Diamond Proposal Number(s): [16354, 16450] Show Abstract ▼ Abstract: There is an increasingly large amount of interest in metal‐organic frameworks (MOFs) for a variety of applications, from gas sensing and separations to electronics and catalysis. Their exciting properties arise from their modular architectures, which self‐assemble from different combinations of metal‐based and organic building units. However, the exact mechanisms by which they crystallize remain poorly understood, thus limiting any realisation of real “structure by design”. We report important new insight into MOF formation, gained using in situ X‐ray diffraction, pH and turbidity measurements to uncover for the first time the evolution of metastable intermediate species in the canonical zeolitic imidazolate framework system, ZIF‐8. We reveal that the intermediate species exist in a dynamic pre‐equilibrium prior to network assembly and, depending on the reactant concentrations and the progress of reaction, the pre‐equilibrium can be made to favour under‐ or over‐coordinated Zn‐imidazolate species, thus accelerating or inhibiting crystallization, respectively. We thereby find that concentration can be effectively used as a synthetic handle to directly control particle size, with great implications for industrial scale‐up and gas sorption applications. These finding enables us to rationalise the apparent contradictions between previous studies of ZIF‐8 and, importantly, opens up new opportunities for the control of crystallization in network solids more generally, from the design of local structure to assembly of particles with precise dimensions.	Nov 2018

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