Synthesis and Characterization of a Layered Silicogermanate PKU-22 and Its Topotactic Condensation to a Three-Dimensional STI-type Zeolite
Journal
Crystal Growth & Design
Journal Volume
17
Journal Issue
10
Pages
5465-5473
Date Issued
2017
Author(s)
Chen, Yanping
Huang, Shiliang
Wang, Xiaoge
Zhang, Lei
Wu, Ningning
Liao, Fuhui
Wang, Yingxia
Abstract
A new layered silicogermanate, PKU-22, was hydrothermally synthesized under fluoride conditions using the tetraethylammonium (TEA+) cation as the structure directing agent (SDA). The crystal structure was determined by single crystal X-ray diffraction. Structure analysis reveals that PKU-22 is constructed by sti layers stacking along the [100] direction in an ···AAAA··· manner, with TEA+ cations occurring in the interlayer spaces and F– anions residing within the layer and connecting to Ge atoms, which also act as the charge compensation species. In situ temperature-variable powder X-ray diffraction results indicated that PKU-22 could be transferred into a three-dimensional STI-type zeolite PKU-22a on heating. It is interesting that the TEA+ cations remain intact in the structure of the condensed product. Solid-state NMR, inductively coupled plasma atomic emission spectroscopy, thermogravimetric-differential scanning calorimetry, and carbon, hydrogen, and nitrogen elemental analyses were applied to aid the structure analysis of PKU-22 and illustrate its transformation. The scheme of the topotactic condensation of PKU-22 to PKU-22a is proposed.
Type
journal article