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, H2TzA = 1H-tetrazole-5-acetic acid),
{[Cd5(MTz)9]·OH}n (2, MTz = 5-methyltetrazolate), and
[Cd3(MTz)3Cl3]n (3) were synthesized via the reactions of a tetrazole
ligand
H2TzA 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 H2TzA ligand.
Single-crystal X-ray diffraction analyses revealed that 1 possessed an infinite 2D layer structure with a μ3-TzA2– moiety, forming a 44-sql topology, and the 2D sheets were further hydrogen-bonded to form
a 3D framework. Compound 2 had a 3D porous framework
with a 49·66-acs topology. Compound 3 adopted a 3D porous
framework with a body-centered cubic (bcu) topology,
which was comprised of 48-membered (Cd24Cl24) rings, and it demonstrated a moderate adsorption of H2 over N2 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.