The synthesis, structures and reactions of zinc and cobalt metal-organic frameworks incorporating an alkyne-based dicarboxylate linker

The reaction of zinc(II) nitrate and 4,4'-ethynylenedibenzoic acid (H(2)edb) in DMF at 80 degrees C gave the metal-organic framework material [Zn4O(edb)(3)(H2O)(2)]center dot 6DMF 1 in which edb ligands connect Zn4O centres into a doubly-interpenetrated cubic network with a similar topology to observed with other linear dicarboxylates in the IRMOF series. Analysis of the nitrogen isotherm revealed the material to have a BET surface area of 1088 m(2) g(-1), which is approximately one-third of the value calculated from GCMC simulations, suggesting incomplete activation or pore blocking in the activated material. The reaction of cobalt(II) nitrate and H(2)edb in DMF gave [Co-3(edb)(3)(DMF)(4)]center dot 2.6DMF 2. The structure of 2 is based on Co-3(O2CR)(6) linear secondary building units that are linked by the edb ligands into a two-dimensional network. When 2 was placed under vacuum, a colour change from pale pink to deep blue was observed, which is consistent with loss of the coordinated DMF molecules. When treated with [Co-2(CO)(8)], crystals of 1 turned dark red, and IR analysis is consistent with coordination of Co-2(CO)(6) fragments to the alkyne groups. However, the colour change was restricted to the external crystal surfaces. This is a likely consequence of partial framework collapse, which occurs following coordination of Co-2(CO)(6) to the alkyne groups. Coordination changes the preferred angle between carboxylate groups in the edb ligand, which in turn introduces strain into the network.