Methylamine as true template and TEAOH as purifying agent: unexpected roles of current organic additives in the hydrothermal synthesis of microporous aluminophosphates

摘要

Methylamine (MA), TEA~+ and water were shown to play a concerted role during the synthesis of two new aluminophosphates IST-1 and IST-2. Both structures start to nucleate after the dramatic change of the gel composition due to preliminary interactions between TEA~+ cations, part of MA and the negative aluminophosphate sheets formed in the clear solution yielding soluble [Al(OH)_x(HPO_4)(H_2O)_y]~- - [TEA,HMA]~+ assemblages that could be identified and formulated by liquid phase ~(13)C-, Al- and ~(31)P-NMR. This in situ complexation is the key parameter for the further nucleation of pure crystalline AlPO_4 phases that readily interact with water and remaining MA in the new altered gel, to get stabilized during growth. As demonstrated, TEA~+ prefer to interact with smaller, probably lamellar (Al-P)-bearing monomeric or oligomeric soluble complexes while water and MA undergo a synergetic pre-arrangement yielding some "super template" assembly that, under favorable experimental conditions, direct and stabilize crystalline IST-1 or IST-2.