Silver nanoparticles loaded pyrazole-based hypercrosslinked microporous polymer for the effective separation of Xe/Kr

The separation of xenon (Xe) and krypton (Kr) from gaseous mixtures is a crucial yet challenging industrial process, primarily due to the inherent inertness and similar physicochemical properties. Herein, we report the synthesis of a novel pyrazole-based microporous organic polymer for efficient Xe/Kr separation. This porous organic polymer possesses abundant nitrogen sites and a concentrated microporous network with pore sizes predominantly centered within the 4–6 Å range. The material exhibited promising Xe adsorption capacity (2.22 mmol·g −1 ) and Xe/Kr Ideal Adsorbed Solution Theory (IAST) selectivity (13.74) at 298 K and 1.0 bar. Furthermore, taking advantage of the strong coordination interactions between the pyrazole groups and metal nanoparticles, silver nanoparticles were successfully introduced to form the composite MOP-PZ-Ag, thereby improving the Xe/Kr separation capability. Under dilute conditions, MOP-PZ-Ag exhibited significantly higher IAST selectivity and Henry's coefficient for Xe compared with MOP-PZ. In dynamic breakthrough experiments, MOP-PZ-Ag showed better separation performance toward Xe/Kr, with the Xe adsorption capacity increasing from 3.79 mmol·kg −1 to 4.91 mmol·kg −1 under low concentration (400 ppm Xe and 40 ppm Kr in dry air). Besides, the superior separation performance of MOP-PZ-Ag can be well maintained over at least five adsorption-desorption cycles. Such experiment results revealed the potential of MOP-PZ-Ag for Xe/Kr separation in used nuclear fuel (UNF) off-gas management.