Xenon (Xe) and krypton (Kr), as the vital noble gases, are widely applied in nuclear energy, aerospace, healthcare and commercial lighting. Developing stable, high-efficiency adsorbents, such as hydrogen-bonded framework (HOFs), for rapid and selective Xe/Kr separation is urgently needed for industrial noble gas purification and nuclear waste gas treatment. However, current HOFs suffer from slow adsorption kinetics and limited dynamic selectivity, severely restricting their practical applications.
In a study published in Angewandte Chemie International Edition, Prof. WU Mingyan from Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, rationally designed and synthesized an ultrastable microporous hydrogen-bonded organic framework (HOF-TBPDM) with unique two-dimensional (2D) interconnected pores, achieving record-high Xe/Kr separation performance and ultra-fast adsorption kinetics.
The researchers found that HOF-TBPDM features size-matched 2D pores and abundant accessible aromatic rings on the pore surface, which exert a stronger polarization effect on Xe than Kr, enabling preferential Xe adsorption. At 298 K and 1 bar, HOF-TBPDM delivers a high Xe uptake of 60.8 cm3 g-1 and a record IAST Xe/Kr selectivity of 26.9, outperforming all reported organic porous materials. Kinetic adsorption tests confirm the 2D pore architecture endows HOF-TBPDM with a rapid Xe diffusion rate (3.09 × 10-6 cm2 s-1), far exceeding that of conventional 1D-pore HOFs.
Dynamic breakthrough experiments show that 4.8 mol kg-1 of high-purity (>99.99%) Kr and 1.0 mol kg-1 of high-purity (>99.9%) Xe can be directly obtained from Xe/Kr mixtures in a single cycle. The dynamic Xe/Kr separation selectivity reaches 16.5, setting a new benchmark for porous organic materials. Notably, HOF-TBPDM maintains excellent separation performance under high gas flow rates, elevated temperatures and long-term air exposure.
Impressively, HOF-TBPDM exhibits exceptional structural stability. It remains intact at 400 °C, in boiling water for seven days, in strong acid/alkali solutions and various organic solvents, a rare property among 2D-pore HOFs. Additionally, it can be rapidly synthesized on a large scale via a simple room-temperature method, with scaled-up samples retaining high crystallinity and separation efficiency identical to single crystals.
This study not only develops an ultrastable HOF with 2D pores for efficient Xe/Kr separation but also provides a universal strategy for designing advanced porous materials with balanced thermodynamic adsorption and kinetic diffusion.
An ultrastable hydrogen-bonded organic framework featuring unique two-dimensional pores demonstrates rapid Xe adsorption kinetics as well as unprecedented dynamic selectivity for Xe/Kr separation.(Image by Prof. WU’s group)
Contact:
Prof. WU Mingyan
Fujian Institute of Research on the Structure of Matter
Chinese Academy of Sciences
Email: wumy@fjirsm.ac.cn
