Gate opening effect for carbon dioxide in ZIF-8 by molecular dynamics – Confirmed, but at high CO2 pressure

Chokbunpiam, T.; Fritzsche, Siegfried; Chmelik, Christian; Caro, Jürgen; Janke, Wolfhard; Hannongbua, Supot

doi:10.1016/j.cplett.2016.01.060

Cited by 40 publications

(55 citation statements)

References 22 publications

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“…The measured CO 2 transport diffusivity in ZIF-7-I (6.3(7) × 10 −9 m 2 s −1 , Fig. 2b) was compared with those experimentally obtained in ZIF-8 at the same temperature (0.4(3) × 10 −9 m 2 s −1 ) 23–26 . We did this comparison because ZIF-8 is an analog of ZIF-7 but has only one type of CO 2 hosting pore (see pore size distribution analysis in Supplementary Fig.…”

Section: Resultsmentioning

confidence: 90%

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Structural dynamics of a metal–organic framework induced by CO2 migration in its non-uniform porous structure

et al. 2019

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Stimuli-responsive behaviors of flexible metal–organic frameworks (MOFs) make these materials promising in a wide variety of applications such as gas separation, drug delivery, and molecular sensing. Considerable efforts have been made over the last decade to understand the structural changes of flexible MOFs in response to external stimuli. Uniform pore deformation has been used as the general description. However, recent advances in synthesizing MOFs with non-uniform porous structures, i.e. with multiple types of pores which vary in size, shape, and environment, challenge the adequacy of this description. Here, we demonstrate that the CO 2 -adsorption-stimulated structural change of a flexible MOF, ZIF-7, is induced by CO 2 migration in its non-uniform porous structure rather than by the proactive opening of one type of its guest-hosting pores. Structural dynamics induced by guest migration in non-uniform porous structures is rare among the enormous number of MOFs discovered and detailed characterization is very limited in the literature. The concept presented in this work provides new insights into MOF flexibility.

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Section: Resultsmentioning

confidence: 90%

“…1 and Supplementary Table 1) connected by six-member-ring windows with similar size (diameter 3.4 – 4.1 Å) and geometry to those of pore A in ZIF-7-I (Supplementary Fig. 6) 14,23 . In contrast, pore B in ZIF-7-I and ZIF-7-II has larger windows of 4.6 – 5.3 Å diameter.…”

Section: Resultsmentioning

confidence: 99%

Structural dynamics of a metal–organic framework induced by CO2 migration in its non-uniform porous structure

et al. 2019

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“…ZIF materials combine the topology and stability of zeolites with the chemical diversity of MOFs. Typical flexibility effect in ZIFs are for example the gate‐opening behavior observed in ZIF‐8, and flexibility of ZIF‐7 and its structural impact in alcohol adsorption . Zheng et al.…”

Section: Zeolite and Mof Force Fieldsmentioning

confidence: 99%

Design, Parameterization, and Implementation of Atomic Force Fields for Adsorption in Nanoporous Materials

Dubbeldam

Walton

Vlugt

et al. 2019

Advcd Theory and Sims

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Molecular simulations are an excellent tool to study adsorption and diffusion in nanoporous materials. Examples of nanoporous materials are zeolites, carbon nanotubes, clays, metal-organic frameworks (MOFs), covalent organic frameworks (COFs) and zeolitic imidazolate frameworks (ZIFs). The molecular confinement these materials offer has been exploited in adsorption and catalysis for almost 50 years. Molecular simulations have provided understanding of the underlying shape selectivity, and adsorption and diffusion effects. Much of the reliability of the modeling predictions depends on the accuracy and transferability of the force field. However, flexibility and the chemical and structural diversity of MOFs add significant challenges for engineering force fields that are able to reproduce experimentally observed structural and dynamic properties. Recent developments in design, parameterization, and implementation of force fields for MOFs and zeolites are reviewed.contain silicon and oxygen. They are readily available, very stable, and relatively cheap. The material should have the right combination of high adsorption selectivity, combined with adequate capacity for use in fixed-bed devices. Recently, new classes of nanoporous materials have been designed that have stability, high void volumes, and well defined tailorable cavities of uniform size. Example are metal-organic frameworks (MOFs), [1][2][3][4][5][6][7] covalent organic frameworks (COFs), [8,9] and zeolitic imidazolate frameworks (ZIFs). [10] These novel materials posses almost unlimited structural variety because of the many combinations of building blocks that can be imagined. The building blocks self-assembly during synthesis into crystalline materials that, after evacuation of the structure, can find applications in adsorption separations, air purification, gas storage, chemical sensing, and catalysis. [4,11] The judicious selection of building blocks allows the pore volume and functionality to be tailored in a rational manner. Because of the designprinciple underlying the synthesis, it is important to understand structure-properties relations, such as the mechanisms of gas separation as a function of shape and size of the pore system, in order to create "blueprints to MOF-design." Computer simulation is cost-effective, fast, and allows for rapid identification of important structural parameters affecting adsorption.Most of the published works on molecular simulation studying zeolites have used the Kiselev model. [12] In this model, zeolite atoms are fixed and interactions of guest atoms with silicon atoms is accounted for by an effective interaction only with the surrounding oxygen atoms. Interactions between sorbate molecules and the host are modeled by placing Lennard-Jones sites and partial charges on all framework atoms and sorbate molecules. The Kiselev model is attractive because of its simplicity and computational efficiency. This model has shown significant success, both in using the molecular dynamics method to compute, for example, the diffu...

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“…The influence of flexibility in MOFs on diffusion has received some attention recently. For example, ZIF-8 was investigated for its flexibility, , and to determine why it is capable of adsorbing molecules with a considerably larger kinetic diameter than the (rigid) pore diameter. , Amirjalayer et al reported that because of the framework flexibility benzene molecules diffuse more slowly through MOF-5 than in the rigid case. Recently, Braun et al investigated multiple thermostats frequently used in molecular dynamics simulations.…”

Section: Introductionmentioning

confidence: 99%

Diffusion of Water and Carbon Dioxide and Mixtures Thereof in Mg-MOF-74

2018

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Self-diffusion coefficients for CO 2 , H 2 O, and mixtures thereof in Mg-MOF-74 have been determined using molecular simulations. The crystal structure was modeled in a rigid and flexible manner with the intent to identify the impact of the flexibility of the framework on the diffusivity. The results show that especially at low loadings the mobility of the molecules is enhanced in flexible lattices because of a small difference in adsorption energy and the enlarged equilibrium distance to the main adsorption sites. In mixtures the flexibility has the same influence; however, because of the presence of the secondary species, water is predominantly located in the close proximity of the magnesium-ion which effectively leads to a segregation effect from the more freely moving CO 2 .

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Gate opening effect for carbon dioxide in ZIF-8 by molecular dynamics – Confirmed, but at high CO2 pressure

Cited by 40 publications

References 22 publications

Structural dynamics of a metal–organic framework induced by CO2 migration in its non-uniform porous structure

Structural dynamics of a metal–organic framework induced by CO2 migration in its non-uniform porous structure

Design, Parameterization, and Implementation of Atomic Force Fields for Adsorption in Nanoporous Materials

Diffusion of Water and Carbon Dioxide and Mixtures Thereof in Mg-MOF-74

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