Synthesis of a new organically templated zeolite-like zirconogermanate (C4N2H12)[ZrGe4O10F2] with cavansite topology

Abstract

A new three-dimensional (3D) zeolite-type zirconogermanate, (C₄N₂H₁₂)[ZrGe₄O₁₀F₂] (designated as FDZG-1), with a low framework density of 13.5 T/1000 ų, has been hydrothermally synthesized by using organic piperazine as template and the inorganic salt ZrO(NO₃)₂·2H₂O as the zirconium source at 160 °C in a mixture of pyridine and water as solvent. Single-crystal X-ray analysis reveals that its framework structure is constructed from a spiro-5 second building unit (SBU) or a parallelepiped-like building block and has a similar topology to cavansite (Ca(VO)Si₄O₁₀·4H₂O). Large elliptic 10-membered ring channels are clearly observed along the crystallographic c axis and blocked by terminal fluorine atoms. Diprotonated piperazinium cations are located in the cavity center of its parallelepiped building block and form strong hydrogen bonds with oxygen atoms and fluorine atoms in the framework. This compound is not stable towards thermal removal of the organic template at above 350 °C.