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

Abstract

A series of heterometal substituted gallium phosphates, (N 2C 4H 7) 0.5+ x [Me 0.5+ x Ga 2.5− x (PO 4) 3] (Me = Mn, Fe, Co and Zn, x ≈ 0.25), has been synthesised under solvothermal conditions at 433 K in ethylene glycol using 1-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 × 13 × 15 Å and β = 112 °, 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)[MeGa 2(PO 4) 3] (Me = Mn, Fe, Co and Zn; T = C 5H 5N and C 3N 2H 4). The size, shape and charge of the amine clearly influence both the metal-phosphate framework stoichiometry (i.e. Me 2+:Ga 3+ ratio) and the framework charge.