Computational structure characterisation tools in application to ordered and disordered porous materials

Sarkisov, Lev; Harrison, Alex G.

doi:10.1080/08927022.2011.592832

Cited by 568 publications

(500 citation statements)

References 27 publications

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“…Effect of pore structure on the selectivity for CH 4 We noticed that the selectivity for methane in smaller pores (width < 1.2 nm) was remarkably higher, which is due to the reduction in entropy of hydrogen molecules and also due to the very high zero point energy of methane molecules in smaller pores.…”

Section: Introductionmentioning

confidence: 95%

Molecular simulations to study the effect of pore geometry and structure on the adsorption of CH4/H2 mixtures in carbon pores

2011

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We used molecular simulations to study the effect of pore structure and geometry on the selectivity of carbon materials for the adsorption of methane from a mixture of methane and hydrogen at 50 bar and 298 K. We modeled hydrogen as a more realistic dumb-bell shaped fluid and methane as spherical Lennard-Jones sphere. The pore geometry studied includes the slit, nanotube, random carbon structure and carbon pores that mimic a foam structure. Our results confirm that both the pore size and pore structure have a significant effect on the selectivity for methane molecules. An array of nanotubes that have a closed structure has the highest selectivity for methane molecules, followed by carbon foam, slit and random pore structures. Energetic and packing effects at low and high pressures, respectively, influence the selectivity for methane. Reduction in entropy of hydrogen in smaller pores increases the selectivity for methane molecules.

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Section: Introductionmentioning

confidence: 95%

Molecular simulations to study the effect of pore geometry and structure on the adsorption of CH4/H2 mixtures in carbon pores

2011

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“…Geometric surface areas can be calculated by using a simple MC integration technique in which a nitrogen probe (3.681 Å ) molecule is rolled along the surface of the framework. [26,76,77] Walton and Snurr provided compelling evidence for the importance of calculating the BET surface area from the proper region of the adsorption isotherm. [75] Commercial 'BET' instruments are typically set to automatically choose a fixed range for BET fitting.…”

Section: Surface Area Void Fraction and Pore-size Distributionmentioning

confidence: 99%

“…The operator must ensure that the range results in consistent BET model parameters. The pore-size distribution (PSD) can be calculated geometrically in RASPA using the method of Gelb and Gubbins [77,78]. For every point in the void volume, the largest sphere is found that encloses the point but does not overlap with any framework atoms.…”

Section: Surface Area Void Fraction and Pore-size Distributionmentioning

confidence: 99%

RASPA: molecular simulation software for adsorption and diffusion in flexible nanoporous materials

Dubbeldam

Calero

Ellis

et al. 2015

Molecular Simulation

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A new software package, RASPA, for simulating adsorption and diffusion of molecules in flexible nanoporous materials is presented. The code implements the latest state-of-the-art algorithms for molecular dynamics and Monte Carlo (MC) in various ensembles including symplectic/measure-preserving integrators, Ewald summation, configurational-bias MC, continuous fractional component MC, reactive MC and Baker's minimisation. We show example applications of RASPA in computing coexistence properties, adsorption isotherms for single and multiple components, self-and collective diffusivities, reaction systems and visualisation. The software is released under the GNU General Public License.

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“…This concept is essentially the same as the one proposed in a recent theoretical work, where linker removal was suggested as a potential method to increase the MOF pore volume and surface area. 29 Indeed, for a perfect UiO-66 crystal, the theoretical pore volume and surface area are modest: 0.426 cm 3 /g and 954 m 2 /g, respectively. For a crystal with 1 out of 12 linkers artificially removed for every metal center in the unit cell (i.e., a hypothetic model structure with ordered defects), the calculated values increase significantly to 0.502 cm Inspired by this observation, in this section we investigated whether the porosity of UiO-66 can be further enhanced by tuning the missing-linker defects.…”

Section: Journal Of the American Chemical Societymentioning

confidence: 99%

Unusual and Highly Tunable Missing-Linker Defects in Zirconium Metal–Organic Framework UiO-66 and Their Important Effects on Gas Adsorption

et al. 2013

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UiO-66 is a highly important prototypical zirconium metal−organic framework (MOF) compound because of its excellent stabilities not typically found in common porous MOFs. In its perfect crystal structure, each Zr metal center is fully coordinated by 12 organic linkers to form a highly connected framework. Using high-resolution neutron power diffraction technique, we found the first direct structural evidence showing that real UiO-66 material contains significant amount of missing-linker defects, an unusual phenomenon for MOFs. The concentration of the missinglinker defects is surprisingly high, ∼10% in our sample, effectively reducing the framework connection from 12 to ∼11. We show that by varying the concentration of the acetic acid modulator and the synthesis time, the linker vacancies can be tuned systematically, leading to dramatically enhanced porosity. We obtained samples with pore volumes ranging from 0.44 to 1.0 cm 3 / g and Brunauer−Emmett−Teller surface areas ranging from 1000 to 1600 m 2 /g, the largest values of which are ∼150% and ∼60% higher than the theoretical values of defect-free UiO-66 crystal, respectively. The linker vacancies also have profound effects on the gas adsorption behaviors of UiO-66, in particular CO 2 . Finally, comparing the gas adsorption of hydroxylated and dehydroxylated UiO-66, we found that the former performs systematically better than the latter (particularly for CO 2 ) suggesting the beneficial effect of the −OH groups. This finding is of great importance because hydroxylated UiO-66 is the practically more relevant, non-air-sensitive form of this MOF. The preferred gas adsorption on the metal center was confirmed by neutron diffraction measurements, and the gas binding strength enhancement by the −OH group was further supported by our firstprinciples calculations. ■ INTRODUCTIONMetal−organic frameworks (MOFs), consisting of inorganic metal centers connected by organic linkers, are a relatively new family of porous materials that possess rich chemistry and offer great promise for gas adsorption related applications.

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Computational structure characterisation tools in application to ordered and disordered porous materials

Cited by 568 publications

References 27 publications

Molecular simulations to study the effect of pore geometry and structure on the adsorption of CH4/H2 mixtures in carbon pores

Molecular simulations to study the effect of pore geometry and structure on the adsorption of CH4/H2 mixtures in carbon pores

RASPA: molecular simulation software for adsorption and diffusion in flexible nanoporous materials

Unusual and Highly Tunable Missing-Linker Defects in Zirconium Metal–Organic Framework UiO-66 and Their Important Effects on Gas Adsorption

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