Dinuclear Nickel–Oxygen Cluster-Based Metal–Organic Frameworks with Octahedral Cages for Efficient Xe/Kr Separation
Jingzhe Wang, Xing-Ping Fu, Qing‐Yan Liu, Ling Chen, Lan-Ping Xu, Yu‐Ling Wang
Abstract
Xe/Kr separation is industrially important but remains a daunting issue in chemical separations. Herein, a fluorinated metal–organic framework (MOF), [Ni2(μ2-O)(TFBPDC)(tpt)2]n (named JXNU-13-F), built from 3,3′,5,5′-tetrakis(fluoro)biphenyl-4,4′-dicarboxylic (TFBPDC2–) and 2,4,6-tri(4-pyridinyl)-1,3,5-triazine (tpt) ligands is provided. JXNU-13-F displays a three-dimensional (3D) framework constructed from distorted octahedral cages and an impressive Xe capacity of 144 cm3 g–1 at 273 K and 1 bar, ranking among top MOFs. The high Xe uptake and moderate Xe/Kr adsorption selectivity endow JXNU-13-F with efficient Xe/Kr separation demonstrated by experimental column breakthrough tests. The comparative studies of gas adsorption between isostructural JXNU-13-F and JXNU-13 (the nonfluorinated analogue ([Ni2(μ2-O)(BPDC))(tpt)2]n with biphenyl-4,4′-dicarboxylic (BPDC2–)) revealed that the F groups serve as the innocent groups during the Xe and Kr adsorption in JXNU-13-F. Thus, a combination of highly hydrophobic and π-electron-rich pore surfaces made of aromatic rings with strong interactions with the Xe atom possessing large polarizability and appropriate pore sizes that match well Xe having a large atom diameter has resulted in high Xe uptake and effective Xe/Kr separation characteristics of JXNU-13-F.