Metal-Organic Frameworks Possessing Suitable Pores for Xe/Kr Separation

Area of Science:

• Materials Science
• Chemical Engineering
• Separation Science

Background:

• Separating xenon (Xe) and krypton (Kr) is challenging due to their similar atomic sizes and inert chemical nature.
• Current separation methods often lack efficiency and selectivity for Xe/Kr mixtures.

Purpose of the Study:

• To investigate the efficacy of novel metal-organic frameworks (MOFs) for Xe/Kr adsorption separation.
• To compare the performance of a chlorinated MOF (JXNU-19(Cl)) with its nonchlorinated analogue (JXNU-19).

Main Methods:

• Synthesis of isostructural MOFs, JXNU-19(Cl) and JXNU-19, based on cobalt-hydroxyl clusters.
• Experimental measurement of Xe/Kr adsorption capacities and selectivities.
• Computational simulations to elucidate Xe binding sites within the MOF structures.

Main Results:

• JXNU-19 exhibited significantly enhanced Xe uptakes and a Xe/Kr adsorption selectivity of 17.1.
• JXNU-19(Cl) showed lower Xe adsorption and selectivity compared to JXNU-19.
• Computational analysis indicated that chlorine sites negatively impacted Xe adsorption in JXNU-19(Cl).

Conclusions:

• The nonchlorinated MOF, JXNU-19, is highly effective for Xe/Kr separation due to optimal pore structure, high surface area, and strong Xe-framework interactions.
• Introducing chlorine groups into the MOF structure can hinder Xe adsorption, reducing separation efficiency.