Metal-Organic Frameworks Featuring 18-Connected Nonanuclear Rare-Earth Oxygen Clusters and Cavities for Efficient...

Two rare-earth (RE) metal-organic frameworks (MOFs) formulated as {(Me₂NH₂)₂[RE₉(μ₃-OH)₈(μ₂-OH)₃(DCPB)₆(H₂O)₃]} (RE = Y³⁺ and Tb³⁺; termed JXNU-10) built from a triangular 3,5-di(4'-carboxylphenyl)benzoic acid (DCPB^3-) ligand are presented. JXNU-10 features the rarely observed 18-connected nonanuclear [RE₉(μ₃-OH)₈(μ₂-OH)₃] clusters, one-dimensional-nanosized tubular channels, and trigonal-bipyramidal cavities. The presence of the high-nuclear RE-oxo clusters and the robust coordination bonds between the highly charged RE ions and the hard base of the carboxylate/hydroxyl oxygen atoms yielded the water-resistant JXNU-10 materials. JXNU-10 exhibits highly selective sorption of C₂H₂ over CO₂ and highly efficient separation of a C₂H₂ and CO₂ mixture. The carboxylate oxygen atoms and the rich π systems of the organic ligands on the pore walls are the desirable binding sites for a C₂H₂ molecule with acidic hydrogen atoms and an alkyne group, facilitating the excellent efficiency of JXNU-10 for C₂H₂/CO₂ separation demonstrated by breakthrough experiments.