The influence of metal ions on the synthesis of MeAPO-5 (Me=Co, Mg) in the presence of acetate ions

Metal-substituted type 5 aluminophosphate structures have been prepared hydrothermally in a buffer solution consisting of acetic acid and a high concentration of template. The acetate ion added to the reaction mixture decreases the interaction of the metal ions with the gel and keeps the initial pH of the mother liquor. There was almost no change in the pH of the reaction mixture during the preparation. The most suitable pH range to synthesize single crystals of MeAPO-5 (Me=Co, Mg) was found to be around pH 5.5. The morphologies of the as-synthesized MeAPO-5 crystals were strongly dependent on the pH of the solution. The size of the crystals increased with increasing metal contents. Owing to the roles of acetate ions, MeAPO-5 crystals were obtained at high concentrations of template and metal ion. Increasing the amount of water and reducing the reaction temperature resulted in the formation of CHA-type structures.