Versatile Rare Earth Hexanuclear Clusters for the Design and Synthesis of Highly-connected ftw-MOFs

A series of highly porous MOFs were deliberately targeted to contain a 12-connected rare earth hexanuclear cluster and quadrangular tetracarboxylate ligands. The resultant MOFs have an underlying topology of ftw, (4, 12)-c ftw-MOFs. This targeted RE ftw-MOF platform offers potential to assess the effect of pore functionality and size, via ligand functionalization and/or expansion, on adsorption properties of relevant gases. Examination of gas adsorption properties of these compounds showed that the ftw-MOF-2 analogues, constructed from rigid ligands having a phenyl, a naphthyl or an anthracene core, exhibited a relatively high degree of porosity. The specific surface areas and pore volumes of these analogs are amongst the highest reported for rare earth based MOFs. Further studies reveal that Y-ftw-MOF-2 shows promising attributes as a storage media for methane (CH4) at high pressures. Furthermore, Y-ftw-MOF-2 shows potential as a separation agent for the selective removal of normal butane (n-C4H10) and propane (C3H8) from natural gas (NG) as well as interesting properties for the selective separation of n-C4H10 from C3H8 or isobutane (iso-C4H10).