Sculpting the Pores of a Metal–Organic Framework using Encapsulated Polyoxometalates for Enhanced Xe/Kr Separation

Postsynthetic modification (PSM) of metal–organic frameworks (MOFs) is an attractive approach for enhancing the functionality and boosting the performance of these nanoporous materials. The few prior studies exploiting PSM for enhanced Xe/Kr separation have relied on elaboration of either the metal nodes or the organic linkers of candidate MOFs. Herein, we introduce an alternative approach, sculpting the pores of a zirconium-based MOF, NU-903, with a size-matching Keggin polyoxometalate (POM). The computationally optimized structure of POM@NU-903 showed that the original 3-dimensional pore was sculpted to a 2-dimensional network-like pore. Although the pore volume decreased by 20%, Xe and Kr uptake capacities were nearly doubled at 298 K and 1 bar, with significantly boosted selectivity and heat of adsorption. Given the agreement between computational and experimental results and the great variety of MOFs and POMs, we envision a sizable library of pore-sculpted MOFs for demonstration and optimization of desired chemical separations.