Pore Size Reduction by Methyl Function in Aluminum-Based Metal–Organic Frameworks for Xenon/Krypton Separation

The design and construction of radioactive stable metal–organic frameworks (MOFs) are highly desirable for noble gases (Xe and Kr) separation from off-gas steams during used nuclear fuel reprocessing under radiation environments. Al-based MOFs are promising for realistic applications of Xe/Kr separation due to their high hydrothermal and chemical stability and comparatively easy and massive preparation by nonpoisonous, abundant, and cheap metal. Herein, we report on two isoreticular microporous Al-MOFs Al-Fum (Al-fumarate, Basolite A520) and Al-Fum-Me (Al-methyl-fumarate) with high radioactive stability for Xe/Kr separation. Appending methyl groups on the framework provides an effective approach to reduce and fine-tune the pore size of Al-Fum-Me to match well with the Xe atom and remarkably improve the framework-Xe affinity. Al-Fum-Me exhibits significantly enhanced Xe/Kr separation performance compared to Al-Fum, demonstrated by adsorption isotherms and breakthrough experiments. Gamma-ray irradiation experiments also identified the high radioactive stability of Al-Fum-Me, suggesting its great potential for practical application on Xe/Kr separation.