Isoreticular Three-Dimensional Kagome Metal–Organic Frameworks with Open-Nitrogen-Donor Pillars for Selective Gas Adsorption

Here, we report a double-bent-ligand strategy which addresses a commonly encountered challenge in the construction of pillar-layered structures with corrugated layers which are common for nonlinearly coordinated ligands and low-symmetry chiral ligands. Specifically, we show here that out-of-alignment metal coordination sites between two adjacent and opposing layers caused by in-layer bent-type ligands could be joined by another ligand type with a matching bent angle. Two isoreticular metal–organic frameworks, CPM-63m and CPM-63a, are presented here to illustrate the implementation of this strategy. Specifically, [Zn₂(RCOO)₄] paddlewheel dimers are bridged by bent FDC^2– (H₂FDC = 2,5-furandicarboxylic acid) to form neutral kagome layers. The resulting corrugated layers are successfully pillared by bent MTZ^– (HMTZ = 5-methyltetrazole) or ATZ^– ligands (HATZ = 5-aminotetrazole). Furthermore, the MTZ^– and ATZ^– pillars offer open N-donor sites, and gas sorption studies of N₂, CO₂, CH₄, C₂H₂, C₂H₄, and C₂H₆ show that these materials are highly porous. In addition, they exhibit interesting inverse ethane/ethylene separation properties and good CO₂/CH₄ separation.