Multiscale Computational Screening of Metal–Organic Frameworks for Kr/Xe Adsorption Separation: A Structure–Property Relationship-Based Screening Strategy

Abstract

The separation of radioactive noble gases, such as Xe and Kr, has attracted special attention in the context of used nuclear fuel (UNF). In this study, 180 metal–organic frameworks (MOFs) formally used for selective adsorptions of ethane and ethylene, with a similar kinetic diameter to Kr and Xe, were initially screened for the Kr/Xe separation using the grand canonical Monte Carlo (GCMC) method. Then, the structure–adsorption property relationships were generalized, that is, the MOFs of higher Kr/Xe selectivity are with the porosity at 0.2–0.4 and the ratio of the largest cavity diameter/pore limiting diameter at 1.0–2.4. Based on the relationships, six reported MOFs with large Kr uptakes and Kr/Xe selectivities were experimentally screened out and validated by GCMC simulations within the CoRE-MOF database, which are higher than most reported MOFs under conditions pertinent to nuclear fuel reprocessing of an 80/20 v/v mixture of Kr/Xe at normal temperature and pressure. Further simulations reveal that higher Kr uptakes and Kr/Xe selectivities of six MOFs result from the confinement effect of the pores. Molecular dynamic simulations showed that the six MOFs are ideal membrane separation materials of Kr from Xe, which are driven by adsorption and diffusion. Analyses of electronic structure-based density functional theory calculations showed that the main interaction between Kr and the six MOFs is van der Waals force dominated by dispersion and induction interactions. Therefore, the generalized structure–adsorption property relationships may assist the screening of MOFs for the separation and production of Kr/Xe from UNF industrially.

Kinetic separation of C2H6/C2H4 in a cage-interconnected metal–organic framework: an interaction-screening mechanism

“…15,16 In this regard, molecular dynamic (MD) simulation in combination with Grand Canonical Monte Carlo (GCMC) is a powerful tool to probe the dynamic behaviours of gas molecules in MOFs. [17][18][19] A comprehensive multi-scale simulation would be essential for painting a full picture of the gas adsorption behaviour, locally and globally, kinetically and thermodynamically.…”

Structural Changes from Conventional SrSnO3 to Ruddlesden–Popper Sr2SnO4 Perovskites and Its Implication on Photoluminescence and Optoelectronic Properties

“…Structure–property correlation is one of the most fundamental aspects of material design that needs understanding at the molecular level for achieving excellence for designated applications. − Structure is a multivariate parlance, and it broadly covers several materials’ parameters such as defects, symmetry, distortions, and so forth. ,− Among multifunctional ceramics, the ABX 3 type perovskite is in the realm of scientific investigations owing to its interesting and unique optical, magnetic, catalytic, electrical, electronic, and dielectrics properties. − ,,,− SrSnO 3 in particular has been one of the most explored perovskites in achieving excellence in the area of luminescence, optoelectronics, ferroelectricity, and photocatalysis. − …”

Understanding the Adsorption of Noble Gases in Metal–Organic Frameworks Using Diffuse Reflectance Infrared Fourier Transform Spectroscopy

“…Among all MOF materials tested at Pacific Northwest National Laboratory, Ni/DOBDC and a partially fluorinated MOF with copper (FMOFCu) were shown to have improved Xe and Kr capacities at room temperature relative to previous materials. Apart from MOFs, we also explored other porous materials such as porous organic cage compounds (CC3), which have been shown to outperform Ni/DOBDC and FMOFCu in terms of Xe/Kr capacity when tested under identical conditions. − With these MOFs and organic cage compounds, Xe and Kr at parts-per-million (ppm) concentrations have been removed from air at room temperature with Ni/DOBDC, FMOFCu, and CC3.…”

“…Based on our observations from experiments, several factors influence the selectivity of weakly interacting gases within MOFs. For example, MOFs with unsaturated open metal sites offer stronger adsorbate–MOF interactions; however, these adsorbents are not selective for noble gases when other competing gases (H 2 O, CO 2 , and N 2 ) are present. ,,− Similarly, other MOF attributes studied include ligand polarizability, , hydrophilic and hydrophobic surface functionality, − surface area, ,, pore size, ,, presence of metal nanoparticles, and temperature . Overall, all of these factors play a significant role in the ability of the materials to separate noble gases from each other and the air.…”

“…11,12,14−16 Similarly, other MOF attributes studied include ligand polarizability, 17,18 hydrophilic and hydrophobic surface functionality, 19−21 surface area, 14,22,23 pore size, 10,24,25 presence of metal nanoparticles, 13 and temperature. 8 Overall, all of these factors play a significant role in the ability of the materials to separate noble gases from each other and the air. Given the large diversity of MOFs and several factors influencing their adsorption properties, it is difficult to intuit which preconceived MOF to synthesize and prototypeor how to tune an existing MOF architecturefor the targeted adsorption of a noble gas species.…”