Theoretical model estimation of guest diffusion in metal–organic frameworks (MOFs)

Zheng, Bin; Huang, Kuo‐Wei; Du, Huiling

doi:10.1039/c5ra11325c

Cited by 7 publications

(13 citation statements)

References 23 publications

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“…38 Zheng et al reported recently an alternate approach to extract the energy profile from DFT calculations. 39 Last, Chmelik and Karger analyzed experimentally measured transport and Stefan-Maxwell diffusivities of various guest molecules in ZIF-8 with a TST theory-based model and showed a profound agreement on the concentration dependency of diffusivities. 40 Umbrella sampling is a biased sampling method, involving a reaction coordinate (RC) connecting the two cages related to the jump under study.…”

Section: Simulation Methodologymentioning

confidence: 99%

“…There are numerous approaches reported in the literature for handling the rate calculation, from which we chose to follow the energy profile mapping along the diffusion path, as has been used for benzene in silicalite-1 by Forester and Smith and Kolokathis et al and for various gases in ZIF-8 by Verploegh et al This is usually achieved by the umbrella sampling technique . Zheng et al reported recently an alternate approach to extract the energy profile from DFT calculations . Last, Chmelik and Kärger analyzed experimentally measured transport and Stefan-Maxwell diffusivities of various guest molecules in ZIF-8 with a TST theory-based model and showed a profound agreement on the concentration dependency of diffusivities …”

Section: Simulation Methodologymentioning

confidence: 99%

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Computational Study of ZIF-8 and ZIF-67 Performance for Separation of Gas Mixtures

2017

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ZIF-67, a modification of ZIF-8 framework through Zn substitution with Co, is tested for the first time for the separation of ethylene/ethane mixture using molecular simulations. The framework consists of cages connected with narrow apertures, which exhibit flexibility through a swelling motion, allowing for relatively large penetrants to diffuse. ZIF-67 demonstrates an enhanced separation for the specific mixture. Various computational techniques are employed (conventional molecular dynamics and Monte Carlo simulations, umbrella sampling, and Widom particle insertion), and the separation mechanism is investigated in terms of sorption and diffusion, for both ZIF-8 and ZIF-67. The stiffer bonding of Co with the adjacent N atoms results in a tighter structure and an aperture with smaller size and lower swelling amplitude than ZIF-8. The diffusion results show a clear dependency of the kinetic-driven separation on the aperture flexibility of the different frameworks. The diffusivities of different sized molecules (from He to n-butane) are simulated in both ZIF-8 and ZIF-67 frameworks, and the molecular size is correlated with the aperture’s response variations. A generalized method based on these results is developed which helps the understanding of the sieving mechanism as a function of the penetrant size and of the aperture size and flexibility. This approach provides an efficient screening of modifiable frameworks toward more efficient separations.

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Section: Simulation Methodologymentioning

confidence: 99%

Section: Simulation Methodologymentioning

confidence: 99%

Computational Study of ZIF-8 and ZIF-67 Performance for Separation of Gas Mixtures

2017

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“…4,8 Concurrently, an abundance of theoretical methods and models for diffusion computation have been developed. 5,7,[9][10][11] For zeolitic imidazolate framework 8 (ZIF-8) in particular, 12 two trends of note in guest diffusion have been reported in experiments and simulation. 4,10,11,13,14 First, guests with an alkene skeleton diffuse faster than those with an alkane skeleton.…”

Section: Introductionmentioning

confidence: 94%

“…5,7,[9][10][11] For zeolitic imidazolate framework 8 (ZIF-8) in particular, 12 two trends of note in guest diffusion have been reported in experiments and simulation. 4,10,11,13,14 First, guests with an alkene skeleton diffuse faster than those with an alkane skeleton. Chmelik et al 4 measured the self-diffusion of ethene and ethane in ZIF-8 and found that the former diffuses 5.5 times faster than the latter due to its smaller kinetic diameter, which increases the hopping rate of adsorbates from cage to cage and then enhances the diffusion rate.…”

Section: Introductionmentioning

confidence: 94%

Diffusion as a function of guest molecule length and functionalization in flexible metal–organic frameworks

Zheng

Wang

et al. 2016

Mater. Horiz.

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“…The data shown in Figure c essentially provides a snapshot in time of metalation; concentration profiles like this one can be used to estimate diffusivity constants starting from Fick’s laws. , Such analysis has been performed for porous materials, for example, on methanol diffusion through porous materials, and exponential-like profiles were observed . A model to adequately describe the concentration profile of Figure c would require knowing the surface permittivity of UiO-67 (which would include the kinetics associated with surface barriers) and the equilibrium binding kinetics of the Pt precursor to the bipyridine sites.…”

Section: Resultsmentioning

confidence: 99%

Elemental Depth Profiling of Intact Metal–Organic Framework Single Crystals by Scanning Nuclear Microprobe

et al. 2021

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The growing field of MOF–catalyst composites often relies on postsynthetic modifications for the installation of active sites. In the resulting MOFs, the spatial distribution of the inserted catalysts has far-reaching ramifications for the performance of the system and thus needs to be precisely determined. Herein, we report the application of a scanning nuclear microprobe for accurate and nondestructive depth profiling of individual UiO-66 and UiO-67 (UiO = Universitetet i Oslo) single crystals. Initial optimization work using native UiO-66 crystals yielded a microbeam method which avoided beam damage, while subsequent analysis of Zr/Hf mixed-metal UiO-66 crystals demonstrated the potential of the method to obtain high-resolution depth profiles. The microbeam method was further used to analyze the depth distribution of postsynthetically introduced organic moieties, revealing either core–shell or uniform incorporation can be obtained depending on the size of the introduced molecule, as well as the number of carboxylate binding groups. Finally, the spatial distribution of platinum centers that were postsynthetically installed in the bpy binding pockets of UiO-67-bpy (bpy = 5,5′-dicarboxyy-2,2′-bipyridine) was analyzed by microbeam and contextualized. We expect that the method presented herein will be applicable for characterizing a wide variety of MOFs subjected to postsynthetic modifications and provide information crucial for their optimization as functional materials.

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Theoretical model estimation of guest diffusion in metal–organic frameworks (MOFs)

Abstract: An analytical model was developed to efficiently and accurately estimate the guest diffusivity in flexible metal–organic frameworks (MOFs).

Cited by 7 publications

References 23 publications

Computational Study of ZIF-8 and ZIF-67 Performance for Separation of Gas Mixtures

Computational Study of ZIF-8 and ZIF-67 Performance for Separation of Gas Mixtures

Diffusion as a function of guest molecule length and functionalization in flexible metal–organic frameworks

Elemental Depth Profiling of Intact Metal–Organic Framework Single Crystals by Scanning Nuclear Microprobe

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