A Porous Coordination Polymer Assembled from 8-Connected {Co3II(OH)} Clusters and Isonicotinate: Multiple Active Metal Sites, Apical Ligand Substitution, H2 Adsorptilon, and Magnetism

A microporous coordination polymer, namely, [Co-3(ina)(4)(OH)(C2H5OH)(3)] (NO3)center dot C2H5OH center dot(H2O)(3) ( 1, or MCF-38, ina = isonicotinate), with 8-connected {Co-3(OH)} clusters as the structural secondary building units, has been solvothermally synthesized. The hydroxo-centered Go(H) duster involves multiple active metal sites. The interesting apical ligand substitutions have been directly observed, and the corresponding products of [Co-3(ina)(4)(OH) (G)(x)(H2O)(n)](NO3)center dot G center dot(H2O)(m) (1 superset of PrOH, G = PrOH, x = 2, n = 1, m = 3; 1 superset of BuOH, G = BuOH, x = 2, n = 1, m = 1, and 1 superset of MeOH, G = MeOH, x = 3, n = 0, m = 7) have also been obtained by solvothermal syntheses or crystal-to-crystal transformations. High-pressure H-2 adsorption measurement at 77K reveals that activated I can absorb 2.2 wt % H-2 at 5 bar. The relative H-2 absorption at low pressure (86% of the storage capacity at 1 bar) is higher than the corresponding values reported for some typical porous coordination polymers. The magnetic studies of 1 show a dominant antiferromagnetic coupling between Co(II) ions of intra- and inter-duster.