Radiation-Resistant Kr-Selective MOF With Record Kr/Xe Selectivity at Elevated Pressure

The separation of Kr/Xe from spent nuclear fuel off-gas is critical, yet most current adsorbents exhibit Xe-Kr co-adsorption under elevated pressures, posing challenges for industrial pressure swing adsorption processes. Herein, we present and evaluate a metal-organic framework, CALF-20M-w, engineered for molecular sieving separation of Kr/Xe under industrial pressure conditions. CALF-20M-w possesses a pore size of 3.7 Å, which position between Kr (3.6 Å) and Xe (4.1 Å) kinetic diameters, enables record Kr/Xe uptake ratio (52.2) and selectivity of 4424 at 195 K and 5 bar, surpassing all benchmark materials. GCMC simulations reveal that Kr atoms occupy favorable positions within CALF-20M-w's intersecting channels, while Xe atoms are sterically excluded in the pressure range of 1-30 bar. Dynamic breakthrough separation experiments and PSA simulation show CALF-20M-w can yield >99.9% pure Xe, demonstrating feasibility for radioactive Kr removal from spent nuclear fuel off-gases. Moreover, CALF-20M-w exhibits extreme radiation resistance under β-irradiation (72 kGy/h) and γ-irradiation (240 kGy), outperforming UiO-66 and ZIF-8. CALF-20M-w sets new benchmarks for high-pressure molecular sieving in Kr/Xe separation, offering a highly promising strategy for nuclear waste management and rare gas purification.