Porous metal-organic frameworks with multiple cages based on tetrazolate ligands: Synthesis, structures, photoluminescence, and gas adsorption properties

摘要

Three tetrazolate-based coordination polymers [Mn(TzA)(H_2O) _2]_n (1, H_2TzA = 1H-tetrazole-5-acetic acid), {[Cd_5(MTz)_9]·OH}_n (2, MTz = 5-methyltetrazolate), and [Cd_3(MTz)_3Cl_3] _n (3) were synthesized via the reactions of a tetrazole ligand H _2TzA 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_2TzA ligand. Single-crystal X-ray diffraction analyses revealed that 1 possessed an infinite 2D layer structure with a μ_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.