Combination of POMs and deliberately designed macrocations: a rational approach for synthesis of POM-pillared metal–organic framework

Abstract

Two POM-pillared 3D porous compounds, [Cu^ICu^II(Cu^IIfcz)₂(H₂O)₅(PMo^VI₁₀Mo^V₂O₄₀)]·6H₂O (1) and [Cu^I₂(Cu^IIfcz)₂(H₂O)₂(PMo^VI₈V^V₃V^IV₃O₄₂)]·6H₂O (2) (Hfcz = fluconazole, (1-(2,4-difluorophenyl)-1,1-bis[(1H-1,2,4-triazol-1-yl)methyl]benzyl alcohol) have been constructed based on different polyanions, (Cufcz)₂²⁺ macrocations and copper cations by the hydrothermal method. The (Cufcz)₂²⁺ macrocations link Cu cations to generate a 2D wavelike cationic sheet. Then the POM anions act as pillars to the cationic sheet to form different POM-pillared 3D frameworks. In compound 1, the polyanion exhibits a rare coordination mode and acts as a penta-dentate ligand, which acts as to pillars to the cationic sheet to form an unprecedented 3D (3,4,5,6)-connected open framework with (3·6·7)(3²·6·7³)(3³·4·6²·7³·8)(3⁴·4²·6²·7⁶·8)(3²·6²·7⁶·8⁴·10) topology. In compound 2, polyanions covalently link cationic sheets to extend to an unusual 3D (3,4,6)-connected framework with the (5²·6)(5²·6²·7·9)(5⁴·6⁴·7⁴·9³) topology. To the best of our knowledge, it is the first time that POM-pillared 3D metal–organic frameworks have been realized by combining POMs with deliberately designed macrocations and transition-metal ions, using a rational approach for synthesis of POM-based open metal–organic frameworks. In addition, the electrochemical behaviors of compounds 1 and 2 have been investigated.