3D Racemic Microporous Frameworks and 3D Chiral Supramolecular Architectures Based on Evans–Showell-Type Polyoxometalates Controlled by the Temperature

Four new architectures containing [Co2Mo10H4O38]6– polyoxoanion, [Ln(H2O)7][Ln(H2O)5][Co2Mo10H4O38]·5H2O (Ln = Gd 1; Tb 2), and (NH4)3[Ln(H2O)6][Co2Mo10H4O38]·6H2O (Ln = Gd 3; Tb 4) have been synthesized at different temperatures and characterized by elemental analysis, IR and Raman spectroscopy, TG analysis, powder X-ray diffraction and single crystal X-ray diffraction. Isostructural compounds 1 and 2 obtained at the higher temperature (85 °C), are built up of Evans–Showell-type polyoxoanions [Co2Mo10H4O38]6–, respectively, linked by Gd3+ or Tb3+ cations to form a 3D racemic framework with 1D zigzag channels. From the topological point of view, the 3D net is a rare binodal 4-connected SrAl2 (sra) topology. As far as we know, compounds 1 and 2 represent the first examples of 3D architectures based on Evans–Showell-type polyoxometalate. Interestingly, the stable 3D microporous compounds exhibit selective adsorption ability: adsorbing water and methanol, as well as excellent photocatalytic activity for organic dye degradation under visible light irradiation. When the reaction temperature was decreased to room temperature (25 °C), two chiral species 3 and 4 were obtained, with a monosupporting structure composed of one [Co2Mo10H4O38]6– polyoxoanion and one [Ln(H2O)6]3+ unit. These chiral monosupporting motifs can be connected by strong hydrogen-bonding interactions to form a 3D chiral supramolecular architecture. They crystallize in the chiral space group P21, as conglomerates of two enantiomerically pure crystals. Their absolute configurations were determined by the Flack parameters and solid-state circular dichroism spectroscopy.