Switching Xe/Kr adsorption selectivity in modified SBMOF-1: a theoretical study

Area of Science:

• Materials Science
• Nuclear Engineering
• Computational Chemistry

Background:

• Separating Xenon (Xe) and Krypton (Kr) from used nuclear fuel (UNF) is critical.
• Existing methods lack efficiency at room temperature.
• No reports exist on Kr/Xe separation using MOF adsorption at room temperature.

Purpose of the Study:

• To investigate the adsorption and separation of Kr from Kr/Xe mixtures at room temperature using modified SBMOF-1 materials.
• To explore the effect of metal center modification (Ca to Mg) and functional groups on adsorption properties.
• To provide a theoretical basis for designing efficient MOF-based adsorbents for Kr/Xe separation.

Main Methods:

• Grand Canonical Monte Carlo (GCMC) simulations to evaluate adsorption selectivity and capacity.
• Density Functional Theory (DFT) calculations to understand electronic structure and interaction mechanisms.
• Independent Gradient Model (IGM) and Energy Decomposition Analysis (EDA) to analyze intermolecular forces.

Main Results:

• Mg-SBMOF-1 exhibits extremely high Kr/Xe adsorption selectivity (250,000).
• NH2-modified Mg-SBMOF-1 shows a 300% increase in Kr adsorption capacity (1.020 mmol g⁻¹).
• Stronger electron-donating functional groups enhance Kr adsorption capacity due to increased ligand polarizability.
• Van der Waals forces, primarily induction for Mg-SBMOF-1 and dispersion for modified versions, govern Kr adsorption.

Conclusions:

• Mg-SBMOF-1 is a promising material for efficient Kr/Xe separation at room temperature.
• Functional group modification significantly impacts adsorption performance.
• This theoretical study offers a pathway for experimental synthesis and application in nuclear waste management.