Distribution of trivalent metal cations in alumino-/gallogermanate zeolites with JST topology

Abstract

A series of zeolitic alumino- and gallogermanate compounds, |M(II)(en)₃|[M(III)₂Ge₄O₁₂] (M(II) = Ni, Co, Zn; M(III) = Al, Ga; en = ethylenediamine), has been synthesized using in situ formed [M(II)(en)₃]²⁺ cations as the structure-directing agents. These zeolitic compounds exhibit the same JST framework topology which is built exclusively of 3-rings. Their structures were determined by single-crystal X-ray diffraction. The frameworks of these compounds are constructed from M(III)- and Ge-centred tetrahedra. According to inductively coupled plasma (ICP) analyses, the ratios of M(III)/Ge are 1/2 in all these compounds. The resulting negative charges in these frameworks are compensated by extra-framework [M(II)(en)₃]²⁺ cations. Single crystal structural analyses show that there are two crystallographically distinct atom sites for M³⁺. According to the ICP results and the unique structural feature of JST, the most reasonable distribution of M³⁺ cations in these structures was deduced.