The combination of lightweight metal cations with a range of dicarboxylate ligands has led to the generation of ionic network materials that possess channels occupied by solvent molecules. The compounds [Li2 (2,2-bpdc)(DMF)2 ] and [Mg(2,2-bpdc)(DMF)2 ] (2,2-bpdc=2,2-dipyridyl-4,4-dicarboxylate) adopt a similar structure in which parallel metal-carboxylate chains are linked to four equivalent chains to generate a 3 D network in which DMF molecules occupy channels. [Li4 (3,5-pdc)2 (DMF)]⋅solvate (3,5-pdc=3,5-pyridine dicarboxylate) adopts a similar structure but the chains are more complex. As with the other structures, coordinated DMF molecules occupy network channels. [Li4 (3,5-pdc)2 (DMF)]⋅solvate is able to adsorb carbon dioxide at elevated pressures with the adsorption following a type V isotherm; hysteresis is apparent upon desorption. The final compound, Li[Mg3 OH(2,2-bqdc)3 (DMF/H2 O)3 ]⋅solvate (2,2-bqdc=2,2-biquinoline-4,4-dicarboxylate) has a distinctly different structure in which a trio of magnesium centres bound to a central μ3 -hydroxide ion serves as a 6-connecting, trigonal prismatic node within a 3 D network that has the point symbol, 49 66 . Solvent-filled intraframework spaces represent over 50 % of the crystal volume and are occupied by highly disordered solvent and Li+ ions. Immersion of Li[Mg3 OH(2,2-bqdc)3 (DMF/H2 O)3 ]⋅solvate in a solution of Fe(2,2-bipyridine)3 2+ results in the incorporation of the FeII complex into the large channels of the anionic network.
Keywords: carboxylate ligands; ion exchange; lithium; magnesium; metal-organic frameworks.
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