New reticular chemistry of pillared rare-earth kgd supermolecular building layer frameworks with ethane-trapping property

Abstract

The industrial demand for ethylene is increasing, efficient purification of ethylene from ethane is of significant importance but challenging. Pillar-layered metal–organic frameworks (MOFs) have aroused extensive attention due to their application potential in gas separation, storage and catalysis, etc. Herein, five pillar-layered rare-earth (RE)-MOFs based on rare kgd supermolecular building layers (SBLs) were successfully prepared under solvothermal conditions by means of Tb(NO₃)₃·6H₂O as the metal source, single tritopic H₃NTB (4,4′,4′′-nitrilotribenzoic acid) or mixed H₃NTB, with a series of ditopic ligands with distinct length as the bridge linkers. Single crystal structure analyses show that three types of pillar-layered RE-MOFs were isolated due to the difference of pillars between the exclusive kgd SBLs, i.e., trk, zma and tpk topological networks. The N₂ isotherms exhibit that the first four MOFs feature microporous characteristics. Furthermore, the single component of C₂H₆, C₂H₄, C₂H₂ and CO₂ sorption isotherms show that the four materials exhibit reverse C₂H₆/C₂H₄ separation as well as C₂H₂-selective adsorption for a C₂H₂/CO₂ mixture. Among them, Tb-NTB-1,4-NDC displays the best separation potential as revealed by ideal adsorption solution theory and dynamic column breakthrough experiments.