Boosting Record Xe Uptake for Efficient Xe/Kr Separation under High Humidity in a Cage-Based MOF with Open Metal Sites

Adsorptive separation of xenon (Xe) and krypton (Kr) is a promising yet challenging technique due to their similar physical properties. In this work, we present a microporous metal-organic framework (MOF) with open metal sites exposed on the small caged pores for efficient Xe/Kr separation. The cage-based MOF, Cu-BTA, features well-defined permanent pores and exhibits record-high Xe gravimetric and exceptionally high volumetric uptake capacities of 7.61 mmol g^-1 and 7.54 mmol cm^-3 at 298 K and 100 kPa. Breakthrough experiments confirm its excellent separation performance for 20:80 Xe/Kr mixtures under both dry and highly humid conditions with the highest dynamic Xe uptake of 4.92 mmol g^-1. Moreover, the material demonstrates efficient Xe capture even at an ultralow concentration (400 ppm), suggesting its great potential for removing radioactive Xe from used nuclear fuel (UNF) reprocessing off-gas.