Pressure-Induced Cooperative Bond Rearrangement in a Zinc Imidazolate Framework: A High-Pressure Single-Crystal X-Ray Diffraction Study

Spencer, Elinor C.; Angel, R. J.; Ross, Nancy L.; Hanson, Brian E.; Howard, Judith A. K.

doi:10.1021/ja808531m

Cited by 153 publications

(147 citation statements)

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“…In fact, 'trigonal' Zn centres are characteristic of the upper temperature region and are restored to tetrahedral Zn centres on lowering temperature (227 uC) as indicated by our numerical simulations. The coi-zni transformation mechanism suggested by our MD simulations involves rearrangement of the same Zn-N contacts as proposed recently by Spencer et al 10 for the pressure-induced znicoi transition. Our simulations and experiments now add important mechanistic details about the transition state for the thermally-induced coi-zni transition.…”

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confidence: 80%

“…7 However, up to now there was no experimental study which addressed the important question about the thermodynamically most stable phase(s) ('ground state(s)') in the Zn(im) 2 system, which might be either of the two most dense phases zni or coi. Recently, an irreversible single-crystal-to-single-crystal pressureinduced phase transition from the zni to the coi phase was observed at room temperature by Spencer et al 10 revealing that coi is stable at high pressures (>0.55 GPa). The polymorphs with zni and coi underlying nets crystallise in the tetragonal space groups I4 1 cd and I4 1 , respectively, and are closely related to each other since both frameworks may be considered as being built up from triple helices connected in different ways (Fig.…”

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confidence: 99%

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Subtle polymorphism of zinc imidazolate frameworks: temperature-dependent ground states in the energy landscape revealed by experiment and theory

et al. 2013

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We show by variable-temperature X-ray diffraction and differential scanning calorimetry experiments that zinc imidazolates with coi and zni framework topology, respectively represent the thermodynamically stable phase below and above a transition temperature of #360 uC at ambient pressure. The relative stability of the two polymorphs and the experimentally observed strong negative thermal expansion of the coi phase at high temperatures close to the phase transition were successfully modelled using density functional theory calculations. A novel metastable zinc imidazolate with neb framework topology was detected by in situ X-ray diffraction experiments as a transient crystalline phase during solvothermal crystallisation of the stable coi phase.Zeolitic imidazolate frameworks (ZIFs) represent a new class of technology relevant microporous materials that are at the focus of current research efforts. 1,2 Important characteristics of ZIFs are comparatively high thermal and chemical stabilities and the ability to crystallise in a large variety of topologically different frameworks which may be tailored for a specific application in gas storage, separation, sensing or catalysis. ZIFs consist of tetrahedral cationic centres (Zn II , Co II , Fe II , Cd II , and also Li I /B III ) connected by imidazolate-based bridging ligands. Because of the local tetrahedral geometry of metal connectors and the metal-imidazolatemetal bridging angle of #145u ZIFs adopt network topologies common for microporous silica polymorphs and zeolites. Recent studies have revealed that ZIFs may undergo thermally-and/or pressure-induced amorphisation that reinforces the similarity between ZIFs and silica. [3][4][5] However, important differences between ZIFs and silica systems are still ignored in the literature. For example, it is well known that the thermodynamic 'ground state' of the silica system at ambient conditions corresponds to the a-quartz phase (qtz net) 6 , whereas the quartz-like topology is hardly accessible in the Zn(im) 2 (im = imidazolate) system as was shown in our previous ab initio study. 7,8 By considering only unsubstituted imidazolate bridging ligands, nine topologically different Zn(im) 2 frameworks have been experimentally realised to date (zni, coi, cag, mer, gis, dft, crb, zec, nog) 1,2,9 and even more are predicted to be synthetically accessible. 7 However, up to now there was no experimental study which addressed the important question about the thermodynamically most stable phase(s) ('ground state(s)') in the Zn(im) 2 system, which might be either of the two most dense phases zni or coi. Recently, an irreversible single-crystal-to-single-crystal pressureinduced phase transition from the zni to the coi phase was observed at room temperature by Spencer et al. 10 revealing that coi is stable at high pressures (>0.55 GPa). The polymorphs with zni and coi underlying nets crystallise in the tetragonal space groups I4 1 cd and I4 1 , respectively, and are closely related to each other since both frameworks may be considered ...

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confidence: 99%

Subtle polymorphism of zinc imidazolate frameworks: temperature-dependent ground states in the energy landscape revealed by experiment and theory

et al. 2013

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“…The unique tetrahedral framework structure of ZIF-zni was first determined by Lehnert and Seel and is well documented in the literature. 19,20 ZIF-zni can be prepared by various methods. [19][20][21] We chose to investigate ZIF-zni formation from supersaturated methanol solutions containing Zn(NO 3 ) 2 Á6H 2 O and imidazole (Him) at room temperature, that is, under conditions similar to the above-mentioned ZIF-8 crystallization, arguing that such comparative studies could be particularly helpful to gain detailed understanding of the underlying formation mechanisms of metal imidazolate frameworks.…”

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confidence: 99%

In situ static and dynamic light scattering and scanning electron microscopy study on the crystallization of the dense zinc imidazolate framework ZIF-zni

Hikov

Schröder

Cravillon

et al. 2012

Phys. Chem. Chem. Phys.

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The kinetics and mechanism of crystallization of the dense zinc imidazolate framework with zni topology, from comparatively dilute methanol solutions containing Zn(NO 3 )Á6H 2 O and imidazole with variation of the zinc-to-imidazole ratio, were followed in situ by time-resolved static and dynamic light scattering. The light scattering data revealed that metastable primary particles of about 100 nm in diameter form rapidly upon mixing the component solutions. After a lag time that is dependent on the imidazole concentration, the primary particles aggregate into secondary particles by a monomer addition mechanism with the primary particles as the monomers. Complementary scanning electron microscopy revealed that further evolution of the secondary particles is a complex process involving polycrystalline intermediates, the non-spherical morphologies of which depend on the initial zinc-to-imidazole ratio. Time and location of the first appearance of crystalline order could so far not be established. The pure-phase ZIF-zni crystals obtained after 240 min are twins. The aspect ratio of the tetragonal crystals can be controlled via the zinc-to-imidazole ratio.

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“…It is noteworthy that the measured E value was ≃3 GPa, which is an order of magnitude lower than that expected from density functional theory calculations (13,14); this is thought to be attributed to sample degradation because MOF-5 crystals are particularly moisture sensitive (15). In the case of ZIFs, recent studies have focused on pressure-induced phase transformations under hydrostatic compression in a diamond anvil cell (16)(17)(18), from which their bulk moduli (K) have also been approximated. In fact, our knowledge of the mechanical properties of ZIFs is limited to an estimate of the roomtemperature bulk modulus of a phase with the dense zni topology (zni is the three-letter symbol used to designate network topology; see http://rcsr.anu.edu.au/) [K ≃ 14 GPa (16)], and another for porous ZIF-8 [K ≃ 6.5 GPa (19)].…”

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confidence: 97%

Chemical structure, network topology, and porosity effects on the mechanical properties of Zeolitic Imidazolate Frameworks

Tan

Bennett

Cheetham

2010

Proc. Natl. Acad. Sci. U.S.A.

484

451

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The mechanical properties of seven zeolitic imidazolate frameworks (ZIFs) based on five unique network topologies have been systematically characterized by single-crystal nanoindentation studies. We demonstrate that the elastic properties of ZIF crystal structures are strongly correlated to the framework density and the underlying porosity. For the systems considered here, the elastic modulus was found to range from 3 to 10 GPa, whereas the hardness property lies between 300 MPa and 1.1 GPa. Notably, these properties are superior to those of other metal-organic frameworks (MOFs), such as MOF-5. In substituted imidazolate frameworks, our results show that their mechanical properties are mainly governed by the rigidity and bulkiness of the substituted organic linkages. The framework topology and the intricate pore morphology can also influence the degree of mechanical anisotropy. Our findings present the previously undescribed structuremechanical property relationships pertaining to hybrid open frameworks that are important for the design and application of new MOF materials.elastic properties | metal-organic frameworks | nanohardness | nanoporosity | zeolitic imidazolate frameworks Z eolitic imidazolate frameworks (ZIFs) represent a unique class of metal-organic frameworks (MOFs) in which the network topology and related properties vary greatly while core chemical connectivity is retained (1, 2). ZIFs currently attract considerable interest by virtue of their exciting potential for hydrogen storage and carbon dioxide capture (3, 4). They adopt porous crystalline structures composed of metal ions and organic linkers, ordered in an analogous fashion to that of silicon and oxygen in zeolites. Specifically, tetrahedral metal centers [typically M ¼ ZnðIIÞ or Co(II)] that are solely coordinated by nitrogen atoms in the 1,3-positions of the imidazolate bridging ligand (Im ¼ C 3 N 2 H − 3 ), subtend an angle of 145°at the M-Im-M center (i.e., analogous to the Si-O-Si angle in silicas and zeolites). Such hybrid architectures can, importantly, give rise to a multitude of extended 3D open frameworks with topologies akin to those found in aluminosilicate zeolites. Over 90 distinct ZIF structures based on 36 of these tetrahedral topologies have been discovered thus far (5). Remarkably, ZIFs combine the classical zeolitic traits of chemical and thermal stability with the rich topological diversity and pore size tunability characteristic of MOFs (6, 7).By and large, research into MOF materials has been motivated by the prospect of discovering new structures with enhanced functional properties for use not only in gas adsorption and separation fields, but also in heterogeneous catalysis and molecular sensing applications (8-11). Indeed, all the aforementioned applications involve subjecting the porous systems to various modes of mechanical stresses and strains, for which their mechanical properties are critical to reach practical implementations. For instance, the open framework needs to exhibit good stiffness, rigidity, and robu...

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Pressure-Induced Cooperative Bond Rearrangement in a Zinc Imidazolate Framework: A High-Pressure Single-Crystal X-Ray Diffraction Study

Cited by 153 publications

References 30 publications

Subtle polymorphism of zinc imidazolate frameworks: temperature-dependent ground states in the energy landscape revealed by experiment and theory

Subtle polymorphism of zinc imidazolate frameworks: temperature-dependent ground states in the energy landscape revealed by experiment and theory

In situ static and dynamic light scattering and scanning electron microscopy study on the crystallization of the dense zinc imidazolate framework ZIF-zni

Chemical structure, network topology, and porosity effects on the mechanical properties of Zeolitic Imidazolate Frameworks

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