Separation Of Xenon Research Articles

A Robust fcu-type Yttrium-Based Metal–Organic Framework for Efficient Separation of Xenon and Krypton

A Robust fcu-type Yttrium-Based Metal–Organic Framework for Efficient Separation of Xenon and Krypton

Isoreticular Metal-Organic Frameworks with Aromatic Pores and Dimethylammonium Cations Enable Separation of Light Hydrocarbons and Xenon/Krypton.

The separation of C2-C3 hydrocarbons from methane in natural gas and xenon/krypton purification are crucial yet challenging industrial processes. Herein, we report two isoreticular metal-organic frameworks, ZJU-89 and ZJU-90, featuring aromatic pore environments and dimethylammonium cations, that synergistically enhance the separation of these industrially relevant gas mixtures. ZJU-90 exhibits an exceptional separation performance, achieving C3H8/CH4 and C2H6/CH4 ideal adsorbed solution theory (IAST) selectivities of 1065 and 48, respectively, at ambient conditions, outperforming most reported adsorbent materials. Remarkably, ZJU-90 enables the recovery of >99.95% purity methane from a C3H8/C2H6/CH4 mixture in a single adsorption step. The material also demonstrates the efficient separation of xenon from krypton, even at low concentrations. The superior performance stems from the aromatic rings decorating the pore walls and the free dimethylammonium cations in the channels, which provide an ideal chemical environment for the selective binding of C2H6, C3H8, and Xe through multiple C-H···π interactions and van der Waals forces, as elucidated by theoretical calculations. This work highlights the power of reticular chemistry in designing materials with synergistic pore environments for efficient separations.

Adsorptive separation of Xe/Kr mixtures by microporous lanthanide metal-organic frameworks with high thermal stability

Efficient separation of Xenon (Xe) and Krypton (Kr) is a significant process for their wide industrial applications and potential environmental concerns. Owing to the inert atomic gases (Xe and Kr) nature with similar physical and chemical properties, it is a great challenge to achieve efficient separation of the Xe/Kr mixture. Herein, we report a series of microporous lanthanide based metal-organic frameworks Ln (BTC) (H2O)·(DMF)1.1 (Ln-MOF) (Dy-BTC (1), Er-BTC (2), and Yb-BTC (3)) with ultrahigh thermal stability for adsorptive Xe/Kr separation. These three isostructural Ln-MOFs consisted of lanthanide metal ions and 1,3,5-benzene dicarboxylate ligands that possess a square channel with pore sizes of 6–7 Å. By substitution of Ln ions, Yb-BTC shows the smallest pore size among the three compounds which enables its obvious higher Xe/Kr selectivity compared with the other two Ln-MOFs. Yb-BTC exhibits a moderately high Xe uptake of 2.5 mmol/g (298 K and 1 bar), and a significantly high Xe/Kr uptake ratio of 3.8, indicative of its great potential for separation of Xe/Kr mixture. The effective Xe/Kr separation ability of Yb-BTC was also confirmed by a breakthrough experiment.

Separation of Xenon from Noble Gas Mixtures of Argon, Krypton, and Xenon Using Gas Hydrate Technology

Separation of Xenon from Noble Gas Mixtures of Argon, Krypton, and Xenon Using Gas Hydrate Technology

Programmed Polarizability Engineering in a Cyclen-Based Cubic Zr(IV) Metal-Organic Framework to Boost Xe/Kr Separation.

Efficient separation of xenon (Xe) and krypton (Kr) mixtures through vacuum swing adsorption (VSA) is considered the most attractive route to reduce energy consumption, but discriminating between these two gases is difficult due to their similar properties. In this work, we report a cubic zirconium-based MOF (Zr-MOF) platform, denoted as NU-1107, capable of achieving selective separation of Xe/Kr by post-synthetically engineering framework polarizability in a programmable manner. Specifically, the tetratopic linkers in NU-1107 feature tetradentate cyclen cores that are capable of chelating a variety of transition-metal ions, affording a sequence of metal-docked cationic isostructural Zr-MOFs. NU-1107-Ag(I), which features the strongest framework polarizability among this series, achieves the best performance for a 20:80 v/v Xe/Kr mixture at 298 K and 1.0 bar with an ideal adsorbed solution theory (IAST) predicted selectivity of 13.4, placing it among the highest performing MOF materials reported to date. Notably, the Xe/Kr separation performance for NU-1107-Ag(I) is significantly better than that of the isoreticular, porphyrin-based MOF-525-Ag(II), highlighting how the cyclen core can generate relatively stronger framework polarizability through the formation of low-valent Ag(I) species and polarizable counteranions. Density functional theory (DFT) calculations corroborate these experimental results and suggest strong interactions between Xe and exposed Ag(I) sites in NU-1107-Ag(I). Finally, we validated this framework polarizability regulation approach by demonstrating the effectiveness of NU-1107-Ag(I) toward C3H6/C3H8 separation, indicating that this generalizable strategy can facilitate the bespoke synthesis of polarized porous materials for targeted separations.

Breaking trade-off effect of Xe/Kr separation on microporous and heteroatoms-rich carbon adsorbents

Energy-efficient adsorptive separation of xenon (Xe) and krypton (Kr) based on stable carbon adsorbents is a promising technology. Developing high-capacity adsorbents with excellent selectivity remains a significant challenge. Herein, we report Chlorella-derived heteroatoms-rich microporous carbons with suitable micropore sizes comparable to the kinetic diameter of Xe for highly efficient Xe/Kr separation. The optimized porous carbon, CK-700-1, exhibits high binding affinity for more polarizable Xe, which breaks the trade-off effect by showing benchmark Xe adsorption capacity (5.84 mmol g−1) and excellent Xe/Kr selectivity (13.4) at 298 K and 1.0 bar. Dynamic breakthrough experiments further confirm its practical feasibility for Xe/Kr separation even under low-concentration and humid conditions with excellent cyclability.

Data-mining based assembly of promising metal-organic frameworks on Xe/Kr separation

The adsorptive separation of xenon (Xe) and krypton (Kr) becomes increasingly important for the treatment of used nuclear fuel (UNF), and thus the novel high-performing metal–organic frameworks (MOFs) on Xe/Kr adsorption separation are urgently needed. In this work, the 200 MOFs formally used for ethane/ethylene separation were adapted to construct structure-adsorption property relationships (SAPR) for Xe/Kr mixture (20/80 v/v) at 298 K and 1 bar, to screen for MOFs with large Xe/Kr selectivities and Xe uptakes in the CoRE MOF, G-MOFs and hMOFs databases with more than 320,000 structures. Then based on the screened 1499 MOFs, the important metal nodes and organic linkers of MOFs (genes) governing the Xe uptake were identified by data-mining of feature engineering, which were assembled crossly into three novel promising MOFs according to material genomics strategy. After considering of the regenerabilities, it is found that Xe uptake (4.2857 mmol/g) and Xe/Kr selectivity (19.70) of the assembled Al2O6-fum_B-hmof8_No1 are larger than those of the most of experimentally synthesized frameworks including Al-Fum-Me, overcoming the “trade-off” problem between adsorption selectivity and capacity. From the multiscale calculations at GCMC and DFT levels, it is found that the large 1D pore size that can accommodate a double-atom chain and large electrostatic potential gradient (EPG) should be responsible for the high Xe uptake and Xe/Kr selectivity of Al2O6-fum_B-hmof8_No1, respectively. Note that the present work first report double-atom chain of rare gas adsorbed in MOF materials. The present data mining and cross assembly strategies are expected to assist the discovery of novel high-performing MOF absorbents for the separation of Xe-Kr even light hydrocarbon in the future.

Efficient and selective capture of xenon over krypton by a window-cage metal–organic framework with parallel aromatic rings

Efficient capture and separation of xenon (Xe) and krypton (Kr) from nuclear fuel reprocessing plants is of great significance for the control of discharge of gaseous radioisotopes into the environment. However, due to the similar size and chemically inert spherical properties of Xe/Kr, the discovery of an adsorbent with both high adsorption capacity and high selectivity remains a challenge. Here, we report a microporous MOF (Ni-MOF, [Ni2IINiIII(μ3-OH)(bdc)3(tpt)]·guest) featuring two different cavities with an appropriate triangular hole window size. One is composed of parallel aromatic rings with spacings of approximately 4.3 Å comparable to the kinetic diameter of Xe (4.047 Å), affording excellent binding affinity for Xe while the larger one with narrow pore window provides sufficient space for gas adsorption. The Ni-MOF material exhibits an exceptionally high Xe uptake of 5.43 mmol/g and Xe/Kr selectivity of 7.66 at 298 K and 1 bar. The adsorption capacity is the highest among all MOFs without open-metal-sites. Furthermore, the sorption selectivity of Xe over Kr within Ni-MOF originates from a special sandwiched π-Xe-π interaction revealed by Van der Waals interaction calculations.

Nanoporous 3D Graphene-like Zeolite-Templated Carbon for High-Affinity Separation of Xenon from Krypton

Nanoporous 3D Graphene-like Zeolite-Templated Carbon for High-Affinity Separation of Xenon from Krypton

Balancing uptake and selectivity in a copper-based metal–organic framework for xenon and krypton separation

Efficient separation of Xenon (Xe) and krypton (Kr) is important in the gas industries but remains challenging. Adsorptive separation affords an energy-efficient method to isolate the two noble gases, yet developing selective adsorbents with high uptake and excellent selectivity remains difficult, limited by a trade-off between uptake and selectivity. We report MOF-11 with optimal pore size and accessible open metal sites (OMSs) for separation of Xe over Kr via the discriminable difference in van der Waals interactions. MOF-11 affords a new benchmark for Xe/Kr separation with high Xe uptakes of 4.05 and 4.95 mmol/g (at 0.2 and 1 bar), high Xe/Kr Henry and IAST selectivity (13.6 and 16.1) at 298 K. Evidenced by Xe-loaded structure, multiple Xe···H interactions between Xe and the terminal H atoms allow Xe atoms firmly packed within the framework. This work demonstrates a strategy for balancing uptake and selectivity in Xe/Kr separation by capitalizing on the synergy between optimal pore size and OMSs.

Titelbild: Hydrogen‐Bonded Metal–Nucleobase Frameworks for Efficient Separation of Xenon and Krypton (Angew. Chem. 11/2022)

Wasserstoffgebundene Gerüste , die durch Selbstorganisation von Metall-Nukleobase-Komplexen und Hexafluoranionen entstehen, werden im Forschungsartikel von Wei Zhou, Zongbi Bao et al. vorgestellt (e202117609). In den Kanälen erzeugen die elektronenreichen Anionen in Kombination mit den elektronenarmen Purinringen ein mikroelektrisches Feld, das Xe-Atome polarisiert und einschließt, wodurch eine hocheffiziente Xe/Kr-Trennung unter Umgebungsbedingungen erreicht wird.

Robust and Radiation-Resistant Hofmann-Type Metal-Organic Frameworks for Record Xenon/Krypton Separation.

The discovery of high-performance adsorbents for highly efficient separation of xenon from krypton is an important but challenging task in the chemical industry due to their similar size and inert spherical nature. Herein, we report two robust and radiation-resistant Hofmann-type MOFs, Co(pyz)[Ni(CN)4] and Co(pyz)[Pd(CN)4] (termed as ZJU-74a-Ni and ZJU-74a-Pd), featuring oppositely adjacent open metal sites and perfect pore sizes (4.1 and 3.8 Å) comparable to the kinetic diameter of xenon (4.047 Å), affording the benchmark binding affinity for polarizable Xe gas. These materials thus exhibit both record-high Xe uptake capacities (89.3 and 98.4 cm3 cm-3 at 296 K and 0.2 bar) and Xe/Kr selectivities (74.1 and 103.4) at ambient conditions, all of which are the highest among all the state-of-the-art materials reported so far. The locations of Xe molecules within ZJU-74a-Ni have been visualized by single-crystal X-ray diffraction studies, in which two oppositely adjacent metal centers combined with the right aperture size can construct a unique sandwich-like binding site to offer unprecedented and ultrastrong Ni2+-Xe-Ni2+ interactions with xenon, thus leading to the record Xe capture capacity and selectivity. The excellent separation capacity of ZJU-74a-Pd was verified by breakthrough experiments for Xe/Kr gas mixtures, providing both unprecedentedly high xenon uptake capacity (4.63 mmol cm-3) and krypton productivity (214 cm3 g-1).

Shell‐like Xenon Nano‐Traps within Angular Anion‐Pillared Layered Porous Materials for Boosting Xe/Kr Separation

AbstractAdsorptive separation of xenon (Xe) and krypton (Kr) is a promising technique but remains a daunting challenge since they are atomic gases without dipole or quadruple moments. Herein we report a strategy for fabricating angular anion‐pillared materials featuring shell‐like Xe nano‐traps, which provide a cooperative effect conferred by the pore confinement and multiple specific interactions. The perfect permanent pore channel (4–5 Å) of Ni(4‐DPDS)2MO4 (M=Cr, Mo, W) can host Xe atoms efficiently even at ultra‐low concentration (400 ppm Xe), showing the second‐highest selectivity of 30.2 in Ni(4‐DPDS)2WO4 and excellent Xe adsorption capacity in Ni(4‐DPDS)2CrO4 (15.0 mmol kg−1). Crystallography studies and DFT‐D calculations revealed the energy favorable binding sites and angular anions enable the synergism between optimal pore size and polar porosity for boosting Xe affinity. Dynamic breakthrough experiments demonstrated three MOFs as efficient adsorbents for Xe/Kr separation.

Shell-like Xenon Nano-Traps within Angular Anion-Pillared Layered Porous Materials for Boosting Xe/Kr Separation.

Adsorptive separation of xenon (Xe) and krypton (Kr) is a promising technique but remains a daunting challenge since they are atomic gases without dipole or quadruple moments. Herein we report a strategy for fabricating angular anion-pillared materials featuring shell-like Xe nano-traps, which provide a cooperative effect conferred by the pore confinement and multiple specific interactions. The perfect permanent pore channel (4-5 Å) of Ni(4-DPDS)2 MO4 (M=Cr, Mo, W) can host Xe atoms efficiently even at ultra-low concentration (400 ppm Xe), showing the second-highest selectivity of 30.2 in Ni(4-DPDS)2 WO4 and excellent Xe adsorption capacity in Ni(4-DPDS)2 CrO4 (15.0 mmol kg-1 ). Crystallography studies and DFT-D calculations revealed the energy favorable binding sites and angular anions enable the synergism between optimal pore size and polar porosity for boosting Xe affinity. Dynamic breakthrough experiments demonstrated three MOFs as efficient adsorbents for Xe/Kr separation.

Hydrogen‐Bonded Metal–Nucleobase Frameworks for Efficient Separation of Xenon and Krypton

AbstractXe/Kr separation is an industrially important but challenging process owing to their inert properties and low concentrations in the air. Energy‐effective adsorption‐based separation is a promising technology. Herein, two isostructural hydrogen‐bonded metal–nucleobase frameworks (HOF‐ZJU‐201 and HOF‐ZJU‐202) are capable of separating Xe/Kr under ambient conditions and strike an excellent balance between capacity and selectivity. The Xe capacity of HOF‐ZJU‐201a reaches 3.01 mmol g−1 at 298 K and 1.0 bar, while IAST selectivity and Henry's selectivity are 21.0 and 21.6, respectively. Direct breakthrough experiments confirmed the excellent separation performance, affording a Xe capacity of 25.8 mmol kg−1 from a Xe/Kr mixed‐gas at dilute concentrations. Density functional theory calculations revealed that the selective binding arises from the enhanced polarization in the confined electric field produced by the electron‐rich anions and the electron‐deficient purine heterocyclic rings.

Hydrogen-Bonded Metal-Nucleobase Frameworks for Efficient Separation of Xenon and Krypton.

Xe/Kr separation is an industrially important but challenging process owing to their inert properties and low concentrations in the air. Energy-effective adsorption-based separation is a promising technology. Herein, two isostructural hydrogen-bonded metal-nucleobase frameworks (HOF-ZJU-201 and HOF-ZJU-202) are capable of separating Xe/Kr under ambient conditions and strike an excellent balance between capacity and selectivity. The Xe capacity of HOF-ZJU-201a reaches 3.01 mmol g-1 at 298 K and 1.0 bar, while IAST selectivity and Henry's selectivity are 21.0 and 21.6, respectively. Direct breakthrough experiments confirmed the excellent separation performance, affording a Xe capacity of 25.8 mmol kg-1 from a Xe/Kr mixed-gas at dilute concentrations. Density functional theory calculations revealed that the selective binding arises from the enhanced polarization in the confined electric field produced by the electron-rich anions and the electron-deficient purine heterocyclic rings.

Efficient Xe/Kr separation on two Metal-Organic frameworks with distinct pore shapes

Adsorptive separation of xenon (Xe) from krypton (Kr) is challenging owing to their low concentrations and similar physical properties. Herein, we report two metal–organic frameworks (MOFs) assembled from the same aliphatic ligand (trans-1, 4-cyclohexanedicarboxylic acid, H2CDC), but showing distinct pore shapes. The rhombus pores on Al-CDC show a narrower pore aperture of 4.5 Å × 6.0 Å, contracting to the pseudo-square pores (5.8 Å × 6.8 Å) on Cu-CDC. As a result, Al-CDC exhibits a high Xe adsorption capacity (2.45 mmol g−1) and Xe/Kr selectivity (10.7) at 298 K and 1.0 bar. The confined pore space and abundant saturated C-H groups provide stronger van der Waals interactions toward Xe, which is disclosed by the Grand Canonical Monte Carlo (GCMC) and Density Functional Theory (DFT) calculations. Dynamic breakthrough experiments further confirm their industrial application potential and stable reusability.

A robust metal-organic framework showing two distinct pores for effective separation of xenon and krypton

For Xe/Kr adsorption-based separation, the current process was focused on cryogenic distillation, which is energy intensive. Metal-organic frameworks (MOFs), as an alternative solid state adsorbents, is highly interesting. Here, we reported a new robust MOF (ECUT-51) with two different sizes of pores (pore A and pore B). The excellent Xe/Kr separation ability was attested by dynamic breakthrough experiments. A deep insight into the separation mechanism was further obtained via Grand Canonical Monte Carlo (GCMC) simulation and Density Functional Theory (DFT) calculation. The theoretical calculations unveiled that both Xe and Kr can be accommodated in pore A, while Kr was prohibitive in pore B.

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

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 pot...

Docking of CuI and AgI in Metal–Organic Frameworks for Adsorption and Separation of Xenon

AbstractWe present a metal docking strategy utilizing the precise spatial arrangement of organic struts as metal chelating sites in a MOF. Pairs of uncoordinated N atoms on adjacent pyrazole dicarboxylate linkers distributed along the rod‐shaped Al–O secondary building units in MOF‐303 [Al(OH)(C5H2O4N2)] were used to chelate CuI and AgI with atomic precision and yield the metalated Cu‐ and Ag‐MOF‐303 compounds [(CuCl)0.50Al(OH)(C5H2O4N2) and (AgNO3)0.49Al(OH)(C5H2O4N2)]. The coordination geometries of CuI and AgI were examined using 3D electron diffraction and extended X‐ray absorption fine structure spectroscopy techniques. The resulting metalated MOFs showed pore sizes matching the size of Xe, thus allowing for binding of Xe from Xe/Kr mixtures with high capacity and selectivity. In particular, Ag‐MOF‐303 exhibited Xe uptake of 59 cm3 cm−3 at 298 K and 0.2 bar with a selectivity of 10.4, placing it among the highest performing MOFs.