Porous Metal–Organic\nFrameworks with Multiple\nCages Based on Tetrazolate Ligands: Synthesis, Structures, Photoluminescence,\nand Gas Adsorption Properties

Abstract

Three tetrazolate-based coordination polymers [Mn­(TzA)­(H₂O)₂]_<i>n</i> (<b>1</b>, H₂TzA = 1<i>H</i>-tetrazole-5-acetic acid),\n{[Cd₅(MTz)₉]<b>·</b>OH}_<i>n</i> (<b>2</b>, MTz = 5-methyltetrazolate), and\n[Cd₃(MTz)₃Cl₃]_<i>n</i> (<b>3</b>) were synthesized via the reactions of a tetrazole\nligand\nH₂TzA with metal ions under hydrothermal conditions. During\nthe formation of <b>2</b> and <b>3</b>, Cd­(II) ions were\ncoordinated by MTz^–, which was generated as the\nresult of the in situ decarboxylation of the H₂TzA ligand.\nSingle-crystal X-ray diffraction analyses revealed that <b>1</b> possessed an infinite 2D layer structure with a μ₃-TzA^2– moiety, forming a 4⁴-<b>sql</b> topology, and the 2D sheets were further hydrogen-bonded to form\na 3D framework. Compound <b>2</b> had a 3D porous framework\nwith a 4⁹_<b>·</b>6⁶-<b>acs</b> topology. Compound <b>3</b> adopted a 3D porous\nframework with a body-centered cubic (<b>bcu</b>) topology,\nwhich 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\nluminescent properties of complexes <b>2</b> and <b>3</b> and the corresponding HMTz molecule were also investigated.