Ionothermal synthesis of gallophosphate molecular sieves in 1-alkyl-3-methyl imidazolium bromide ionic liquids

Gallophosphate (GaPO4) molecular sieves were ionothermally prepared in 1-alkyl-3-methyl imidazolium bromide ionic liquids (ILs) with alkyl chain length varying from 2 to 6 carbons for the first time. Three kinds of GaPO4 materials such as GaPO4-a, cloverite (denoted as CLO below) and GaPO4-LTA were obtained, and their structures and morphologies were characterized by powder and single crystal XRD, SEM and multi-nuclear NMR. In the case of 1-ethyl-3-methyl imidazolium bromide ionic liquid, large single crystals Of GaPO4-LTA with well-defined octahedral morphology was obtained in both sealed (ca. 400 mu m in size) and open vessels (ca. 300 mu m in size). Ionothermal synthesis is an effective method for the preparation of large single crystal of molecular sieves. With the alkyl chain length of the ionic liquids increasing from 2 carbons to 6 carbons, the size Of GaPO4-LTA decreased sharply. The organic template cations in the as-synthesized GaPO4-LTA crystals may have two different kinds of conformational structures. Fluorine plays a role of co-template along with organic cations of ILs in the synthesis Of GaPO4-LTA and CLO, while only GaPO4-a was obtained in the absence of fluorine. The reaction temperature can also affect the structure of the final structure. In the reaction medium of 1-ethyl-3-methyl imidazolium bromide IL, GaPO4-LTA was obtained at 180 degrees C, while CLO was obtained at 150 degrees C. Crown Copyright (C) 2008 Published by Elsevier Inc. All rights reserved.