Multiscale adsorption and transport in hierarchical porous materials

Coasne, Benoît

doi:10.1039/c5nj03194j

Cited by 111 publications

(89 citation statements)

References 171 publications

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“…[1,2] Thus, much effort has been made to study such idealizedsystems. [8][9][10][11] It is true that recent progress in PFG NMR methodology [12] has facilitated diffusion studies in also more complex pore architectures [13][14][15][16] just as the investigationof highly heterogeneouss ystemsb eing characterized by ad istribution of diffusivities. [16,17] However,a pplication of such advanced techniques requires high accuracyi nt he spinecho attenuations, which cannotb ee xpectedt ob ea ttainable as ar ule.…”

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confidence: 99%

Assessing Guest‐Molecule Diffusion in Heterogeneous Powder Samples of Metal–Organic Frameworks through Pulsed‐Field‐Gradient (PFG) NMR Spectroscopy

Thoma

Kärger

Amadeu

et al. 2017

Chemistry A European J

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Investigation of guest diffusion in porous metal-organic frameworks (MOFs) is of major importance, because many porosity-related properties of MOFs are influenced by diffusion effects. The diffusion of dimethyl sulfoxide (DMSO) in the MOF MIL-53-NH (Al) was investigated through pulsed-field-gradient (PFG) NMR spectroscopy. The microporous material was synthesized in small crystallites (under 500 nm), which agglomerated in a large range of particle sizes (from hundreds of nanometers to tens of micrometers), giving a morphologically very heterogeneous sample. No special agglomeration pattern could be observed, which makes a PFG NMR investigation very challenging, yet it represents a realistic situation for the diffusion of guest molecules in porous materials. We were able to distinguish between two diffusion regimes existing in parallel with each other over the total range from 15 to 200 ms of observation times as accessible in the experiments: In the large crystal agglomerates (diameters above 20 μm), guest movement was found to be subdiffusive, with a time exponent κ =0.8 (rather than one as for normal diffusion). Guest diffusion in the remaining, smaller host particles followed the pattern of normal diffusion within a bed of spheres of impenetrable external surfaces, with a size distribution in good agreement with that of the material under study. Diffusion in a rather complex system could thus be referred to a two-region model with new potentials for application to systems of intricate topology.

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confidence: 99%

Assessing Guest‐Molecule Diffusion in Heterogeneous Powder Samples of Metal–Organic Frameworks through Pulsed‐Field‐Gradient (PFG) NMR Spectroscopy

Thoma

Kärger

Amadeu

et al. 2017

Chemistry A European J

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“…While in Sections 3.1 and 3.2, resolution enhancement by MAS PFG NMR was exploited for selective diffusion measurement of different components, it may also, equally importantly, be applied for studying the transport patterns of one and the same molecular species in different surroundings. Similarly as in micro-mesoporous hierarchical host materials [64][65][66][67][68][69][70] where guest molecules are known to propagate with different diffusion rates depending on their current position (i.e., within microor transport pores), overall mass transfer in complex systems is often found to occur in a sequence of subsequent displacements covered with different diffusion rates. First-order simulations of mass transfer in such systems are often based on the two-region approach of PFG NMR [71] where the diffusants are implied to diffuse at two different rates D 1,2 , with the respective probabilities p 1,2 and the mean life times τ 1,2 in either of these states [72][73][74][75][76][77].…”

Section: Water Diffusion In Lithium-exchanged Low-silica X-type Zeolitesmentioning

confidence: 99%

Diffusion in Nanoporous Materials: Novel Insights by Combining MAS and PFG NMR

2018

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Pulsed field gradient (PFG) nuclear magnetic resonance (NMR) allows recording of molecular diffusion paths (notably, the probability distribution of molecular displacements over typically micrometers, covered during an observation time of typically milliseconds) and has thus proven to serve as a most versatile means for the in-depth study of mass transfer in complex materials. This is particularly true with nanoporous host materials, where PFG NMR enabled the first direct measurement of intracrystalline diffusivities of guest molecules. Spatial resolution, i.e., the minimum diffusion path length experimentally observable, is limited by the time interval over which the pulsed field gradients may be applied. In “conventional” PFG NMR measurements, this time interval is determined by a characteristic quantity of the host-guest system under study, the so-called transverse nuclear magnetic relaxation time. This leads, notably when considering systems with low molecular mobilities, to severe restrictions in the applicability of PFG NMR. These restrictions may partially be released by performing PFG NMR measurements in combination with “magic-angle spinning” (MAS) of the NMR sample tube. The present review introduces the fundamentals of this technique and illustrates, via a number of recent cases, the gain in information thus attainable. Examples include diffusion measurements with nanoporous host-guest systems of low intrinsic mobility and selective diffusion measurement in multicomponent systems.

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“…Reduction of the diameter of cylindrical nanopores in some zeolites and SiO2 leads to 1D gas behavior in them [5,6]. The change in the behavior of gas and liquid in nanoscale pores compared with their behavior in the free state is largely due to the effect of adsorption [7]. The effect of increase in the volume fraction of gas or liquid molecules in the near-wall region at decreasing nanopore size enhances the influence of the adsorption on the properties and behavior of the substance inside the nanopore [8,9].…”

Section: Introductionmentioning

confidence: 99%

Simulation of benzylpenicillin molecule distribution in slit-shaped Si nanopores

et al. 2019

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A molecular dynamics study of the behavior of benzylpenicillin molecules in slit-shaped nanopores was carried out. A model silicon material with a pore size from 10 to 50 nm was chosen as a nanoporous structure. The interaction between benzylpenicillin molecules was described by a pair potential, built on the basis of modelling the molecule behavior by all-atom force fields. It was shown that an adsorbed layer of benzylpenicillin molecules is formed near the pore walls. With a decrease in the pore size, the maximum density of molecules in the adsorbed layer decreases, while the fraction of adsorbed molecules in the whole pore increases.

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Multiscale adsorption and transport in hierarchical porous materials

Abstract: This review presents the state-of-the-art of multiscale adsorption and transport in hierarchical porous materials.

Cited by 111 publications

References 171 publications

Assessing Guest‐Molecule Diffusion in Heterogeneous Powder Samples of Metal–Organic Frameworks through Pulsed‐Field‐Gradient (PFG) NMR Spectroscopy

Assessing Guest‐Molecule Diffusion in Heterogeneous Powder Samples of Metal–Organic Frameworks through Pulsed‐Field‐Gradient (PFG) NMR Spectroscopy

Diffusion in Nanoporous Materials: Novel Insights by Combining MAS and PFG NMR

Simulation of benzylpenicillin molecule distribution in slit-shaped Si nanopores

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