Tuning the Topology from fcu to pcu: Synthesis and Magnetocaloric Effect of Metal-Organic Frameworks Based on a Hexanuclear Gd(III)-Hydroxy Cluster

Two polynuclear, cluster-based metal-organic frameworks (MOFs), formulated as {H-2[Gd-6(OH)(8)(H2O)(6)(p-BDC-F-4)(6)]center dot 3(2,2'-bpy)center dot 6H(2)O} (1) and {H-2[Gd-6(OH)(8)-(H2O)(6)(m-BDC-F-4)(6)]center dot 3(4,4'-bpy)center dot 6H(2)O} (2) (p-BDC-F-4 = tetrafluoroterephthalic acid, m-BDC-F-4 = tetrafluoroisophthalic acid), are synthesized by hydrothermal reactions of Gd-III ions with perfluorinated benzenedicarboxylate. Structure analysis illustrates that both 1 and 2 are constructed by the hexanuclear Gd-III hydroxy cluster molecular building block {Gd-6(OH)(8)-(COO)(12)(H2O)(6)}, generating a 12-connected fcu-MOF and a 6-connected pcu-MOF, respectively. Compounds 1 and 2 are stable in some refluxing organic solvents, boiling water, and aqueous solutions in the pH range of 2-11. Notably, magnetic investigation indicates that 1 and 2 display a significant magnetocaloric effect.