Control of framework stoichiometry in MeGaPO laumontites using 1-methylimidazole as structure-directing agent

A series of heterometal substituted gallium phosphates, (N2C4H7)(0.5+x)[Me0.5+xGa2.5-x(PO4)(3)] (Me = Mn, Fe, Co and Zn, x approximate to 0.25), has been synthesised under solvothermal conditions at 433 K in ethylene glycol using I-methylimidazole as a templating agent and their structures determined at 150 K using single-crystal X-ray diffraction. The compounds are isostructural, crystallising in the monoclinic space group C 2/c, with lattice parameters ca. 15 x 13 x 15 angstrom and beta = 112 degrees, and adopt the laumontite framework type (LAU). The incorporation of 1-methylimidazole cations into the one-dimensional pore systems of these materials is about three quarters the uptake value obtained previously for the less-bulky amine cations of imidazole and pyridine in other MeGaPO laumontites, which have the formula (TH)[MeGa2(PO4)(3)] (Me = Mn, Fe, Co and Zn; T = C5H5N and C3N2H4). The size, shape and charge of the amine clearly influence both the metal-phosphate framework stoichiometry (i.e. Me2+:Ga3+ ratio) and the framework charge. (C) 2007 Elsevier Inc. All rights reserved.