Porous Metal-Organic Frameworks with Multiple Cages Based on Tetrazolate Ligands: Synthesis, Structures, Photoluminescence, and Gas Adsorption Properties

Three tetrazolate-based coordination polymers [Mn(TzA)(H2O)(2)](n) (1, H(2)TzA = 1H-tetrazole-5-acetic acid), {[Cd-5(MTz)(9)]center dot OH}(n) (2, MTz = 5-methyltetrazolate), and [Cd-3(MTz)(3)Cl-3](n) (3) were synthesized via the reactions of a tetrazole ligand H(2)TzA with metal ions under hydrothermal conditions. During the formation of 2 and 3, Cd(II) ions were coordinated by MTz(-), which was generated as the result of the in situ decarboxylation of the H(2)TzA ligand. Single-crystal X-ray diffraction analyses revealed that 1 possessed an infinite 2D layer structure with a mu(3)-TzA(2-) moiety, forming a 4(4)-sql topology, and the 2D sheets were further hydrogen-bonded to form a 3D framework. Compound 2 had a 3D porous framework with a 4(9).6(6)-acs topology. Compound 3 adopted a 3D porous framework with a body-centered cubic (bcu) topology, which was comprised of 48-membered (Cd-24 Cl-24) rings, and it demonstrated a moderate adsorption of H-2 over N-2 as a result of its limited window size. The solid-state luminescent properties of complexes 2 and 3 and the corresponding HMTz molecule were also investigated.