Adsorptive separation of xenon/krypton mixtures using ligand controls in a zirconium-based metal-organic framework

Lee, Seung Joon; Kim, Seongwoo; Kim, Eun Jung; Kim, Min; Bae, Yang‐Seop

doi:10.1016/j.cej.2017.10.155

Cited by 65 publications

(25 citation statements)

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“…For example, MOFs with high surface area (e.g., IRMOFs, UiO-66) and polar functional groups (e.g., IRMOF-X, UiO-66-X, X = Cl, F, Br, I, NH 2 , etc.) have shown high Xe uptake, but weak gas–adsorbent interactions in these cases have resulted in low gas selectivity. − Additionally, MOFs with accessible, highly polarizable open metal sites (e.g., MOF-74 series, HKUST) have also been evaluated for noble gas separation because of their stronger affinity to Xe than Kr. ,− A number of reports suggest that optimal pore size comparable to the kinetic diameter of Xe is a key factor for high capacity and selectivity. − Among many MOF materials tested for Xe/Kr separation, ,,,− the highest Xe/Kr selectivity has been achieved recently by CROFOUR-1-Ni systems, reaching a value of 22 at 1.0 bar and 298 K …”

Section: Introductionmentioning

confidence: 99%

A Robust Squarate-Based Metal–Organic Framework Demonstrates Record-High Affinity and Selectivity for Xenon over Krypton

et al. 2019

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The efficient separation of xenon (Xe) and krypton (Kr) is one of the industrially important processes. While adsorptive separation of these two species is considered to be an energy efficient process, developing highly selective adsorbent remains challenging. Herein, a rigid squarate-based metal− organic framework (MOF), having a perfect pore size (4.1 Å × 4.3 Å) comparable with the kinetic diameter of Xe (4.047 Å) as well as pore surface decorated with very polar hydroxyl groups, is able to effectively discriminate Xe atoms, affording a record-high Xe/Kr selectivity. An exceptionally high Xe uptake capacity of 58.4 cm 3 /cm 3 and selectivity of 60.6 at low pressure (0.2 bar) are achieved at ambient temperature. The MOF exhibits the highest Xe Henry coefficient (192.1 mmol/g/bar) and Xe/Kr Henry selectivity (54.1) among all state-of-the-art adsorbents reported so far. Direct breakthrough experiments further confirm the excellent separation performance. The density functional theory calculations reveal that the strong interaction between Xe and the framework is a result of the synergy between optimal pore size and polar porosity.

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Section: Introductionmentioning

confidence: 99%

A Robust Squarate-Based Metal–Organic Framework Demonstrates Record-High Affinity and Selectivity for Xenon over Krypton

et al. 2019

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“…Previously Meek et al demonstrated that the IRMOF-2-X series had increased selectivities for the more polarizable monohalogenated linkers . For UiO-type MOFs, Lee et al found that the more donating groups on the linker, the greater the selectivity, while electron-withdrawing groups lower the selectivity . The MOFs studied herein do not follow either of these trends, suggesting that the electronic effects are negligible at these pore size ranges, and the variation in the thermodynamic selectivities only ranges from 4.00 (UiO-68-TMS 2 ) to 4.96 (UiO-68-F 4 ).…”

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confidence: 62%

“…An alternative approach is to take advantage of the differences in the electronic properties of the gases, such as exploiting their difference in polarizability (Figure a), to favor interaction of one gas with the MOF more than with the other. This idea takes advantage of the “heavy atom effect,” where highly polarizable groups interact preferentially with larger atoms (resembling soft–soft interactions). − The only two systematic studies that address these electronic interactions were performed on monohalogenated derivatives of IRMOF-1 (Zn-based) , and functionalized derivatives of UiO-66 (Zr-based) . The IRMOF-1 study showed that, by including highly polarizable iodine as part of the terephthalate link, higher selectivities were achieved than when functionalizing with Br, Cl, or F, and the UiO-66 study showed a positive correlation between Xe/Kr selectivity and polarized ligands.…”

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confidence: 99%

“…32−34 The only two systematic studies that address these electronic interactions were performed on monohalogenated derivatives of IRMOF-1 (Zn-based) 34,35 and functionalized derivatives of UiO-66 (Zr-based). 36 The IRMOF-1 study showed that, by including highly polarizable iodine as part of the terephthalate link, higher selectivities were achieved than when functionalizing with Br, Cl, or F, and the UiO-66 study showed a positive correlation between Xe/Kr selectivity and polarized ligands. While these examples have shown high Xe uptake, they result in lower gas selectivity compared to the previous sterics-based methods.…”

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confidence: 99%

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Steric and Electronic Effects on the Interaction of Xe and Kr with Functionalized Zirconia Metal–Organic Frameworks

Fairchild¹,

Hossain

Córdova³

et al. 2021

ACS Materials Lett.

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The separation of xenon and krypton from their mixtures has been an enduring and complex venture due to their similar sizes and unreactive nature. Metal−organic frameworks (MOFs) have shown the potential to complete these challenging separations by utilizing pressure-swing adsorption (PSA) as a sustainable alternative to current cryogenic distillation techniques. To rationally design materials to better realize this goal, two main approaches have emerged: pore-size optimized and polarizability-based separations. To ascertain the efficacy of these strategies, we designed a series of UiO-type MOFs with terphenyl linkers that systematically varied their steric and electronic properties, including −Me, −F, −TMS, and −I functionalities, to assess their interactions with xenon and krypton. The prepared MOFs are all isoreticular and have similar pore size distributions, allowing us to directly evaluate the effects imposed by the functional groups. We found that the xenon uptake could be increased with greater polarizability of the functional group (−F < −Me ≈ −TMS < −I), whereas the selectivities seem to follow a trend more related to pore-steric effects (−TMS < −I < −Me < −F).

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“…The interaction between Xe and frameworks can be further enhanced by depositing Ag nanoparticles in Ni-MOF-74 with increased Xe capacity by 15.6% 19 . The study on the Xe/Kr separation performances of a series of functionalized UiO-66 materials synthesized by introducing several polar functional groups (-F, -NH 2 , -OMe) revealed that UiO-66-NH 2 (OMe) 2 with the highest electron density exhibited the best Xe/Kr separation performances 20 . The selectivity for Xe/Kr separation of SBMOF-2 and [Co 3 (C 4 O 4 ) 2 (OH) 2 ]•3H 2 O was up to 10 and 69.7 respectively, which was benefited from their suitable pore size and pore surfaces decorated with polar hydroxyl groups 21,17 .…”

Section: Introductionmentioning

confidence: 99%

Porous Hydrogen-Bonded Frameworks Assembled from Metal-Nucleobase Entities for Xe/Kr Separation

et al. 2022

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It is challenging to obtain high-purity xenon (Xe) and krypton (Kr) from the by-products of the air separation process due to their similar atom size and physical properties. Adsorption using porous materials such as metalorganic frameworks has been considered a promising technology to separate Xe/Kr. Herein, we reported two novel isostructural ionic supramolecular metal-organic frameworks (SMOFs, SMOF-PFSIX-1, and SMOF-AsFSIX-1), in which inorganic anions (PF 6or AsF 6-) and cationic metal-organic entities self-assembled through hydrogen bonds to give three-dimension pore channels. The two kinds of SMOFs can separate Xe/Kr efficiently with IAST selectivity of 6.9 and 6.7 under 298 K and 1.0 bar respectively. The breakthrough experiments further confirmed their industrial application potential. The Grand Canonical Monte Carlo (GCMC) and the Density Functional Theory (DFT) calculations revealed that there were multiple adsorptive sites to catch the Xe atom, and the affinity between Xe and frameworks can be attributed to the inorganic anions and amino groups on the ligands. To the best of our knowledge, it was the first time to report the SMOFs for Xe/Kr separation, and we proposed a new strategy for Xe/Kr separation based on the synergistic effect of amino and inorganic anions.

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Adsorptive separation of xenon/krypton mixtures using ligand controls in a zirconium-based metal-organic framework

Cited by 65 publications

References 51 publications

A Robust Squarate-Based Metal–Organic Framework Demonstrates Record-High Affinity and Selectivity for Xenon over Krypton

A Robust Squarate-Based Metal–Organic Framework Demonstrates Record-High Affinity and Selectivity for Xenon over Krypton

Steric and Electronic Effects on the Interaction of Xe and Kr with Functionalized Zirconia Metal–Organic Frameworks

Porous Hydrogen-Bonded Frameworks Assembled from Metal-Nucleobase Entities for Xe/Kr Separation

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