Construction of lanthanide metal–organic frameworks with highly-connected topology based on a tetrapodal linker

Abstract

By using a rigid tetrapodal linker 4,4′,4′′,4′′′-silanetetrayltetrabenzoic acid (H4L) and lanthanide metal ions, three new coordination polymers, namely, [NdL(H2O)][NH2(CH3)2]·(DMF)x·(H2O)y (x ≈ 2, y ≈ 4) (1), [Eu4L3(H2O)6]·(DMF)y·(H2O)x (x ≈ 2, y ≈ 4) (2) and [Er4L3(H2O)6]·(DMF)x·(H2O)z (x ≈ 2, z ≈ 5) (3), were solvothermally synthesized and structurally characterized. Compound 1 is a 3D framework with a (4,8)-connected flu structure, built from distorted cuboid dinuclear neodymium–carboxylate building block and a 4-connected tetrahedral L ligand. Compounds 2 and 3 are isostructural, possessing a non-interpenetrated three-dimensional network with rare (4,4,12) highly-connected topology. In compounds 2 and 3, the fully deprotonated L4− ligands act as pseudotetrahedral 4-connecting nodes and S-shaped tetranuclear lanthanide metal–carboxylate building blocks act as 12-connecting nodes. Compound 1 possesses permanent porosity as confirmed by N2, H2, O2, CO2 and CH4 gas adsorption measurements.