Hydrothermal synthesis and structure of a new layered zincophosphate intercalated with 3-methylaminopropylamine cations

Abstract

A novel layered zincophosphate (ZnPO?MPA) was prepared by hydrothermal crystallization using 3-methylaminopropylamine (MPA) as a structure-directing agent. The structure consists of macroanion [Zn2P3O8(OH)3]2- layers which are built up of 4-membered ring channels. The channels (of about 3.7 ? diameter) arise through the connection of the neighbouring rings by two oxygen bridges. The negative charge of the layers is compensated by diprotonated MPA molecules which are stacked parallel to the ring channels. ZnPO?MPA is stable up to 300 ?C. At higher temperatures MPA decomposition begins followed by a dehydration, which occurs through condensation of the framework hydroxyl groups. The activation energy of the MPA decomposition is high due to the fact that the layers and MPA cations are held together by strong hydrogen bonds.

3-methylaminopropylamine as a templating agent in the synthesis of phosphate-based inorganic polymers

“…Figure 7 shows the FTIR spectra of the ZnPO, AlPO 4 -21, CoAPO-21 and the fluorinated aluminophosphate (APOF). 22 All spectra except that of AlPO 4 -21 display a strong band at about 1540 cm -1 which is attributed to NH 3 + , suggesting that the MPA species was protonated, 8 while the inorganic frameworks of ZnPO, CoAPO-21 and APOF were negatively charged. Vibrations displayed in the range 3200-2000 cm -1 correspond to amine groups, 20 and the bands appearing in the 1600-1350 cm -1 region are due to C-H bonds 21 .…”

“…Vibrations displayed in the range 3200-2000 cm -1 correspond to amine groups, 20 and the bands appearing in the 1600-1350 cm -1 region are due to C-H bonds 21 . 8,12 Thus, MPA entrapped in ZnPO decomposes in a three-step process with the first step having the highest activation energy (343 kJ mol -1 ). 22 All spectra except that of AlPO 4 -21 display a strong band at about 1540 cm -1 which is attributed to NH 3 + , suggesting that the MPA species was protonated, 8 while the inorganic frameworks of ZnPO, CoAPO-21 and APOF were negatively charged.…”