Engineering

Materials science

Layer (electronics)

Crystal structure

Single crystal

Molecule

Chemical engineering

Hydrothermal synthesis

Stereochemistry

Hexagonal crystal system

Nanotechnology

Organic chemistry

Piperazine

Hydrothermal circulation

Characterization (materials science)

Tetrahedron

Crystallography

Chemistry

Octahedron

Group (periodic table)

Ring (chemistry)

Microporous and Mesoporous Materials

Two new two-dimensional-layered aluminophosphates with P:Al=4:3 have been synthesized hydrothermally using 2-methylpiperazine as organic templating molecule, and their structures have been solved using single-crystal X-ray diffraction data. APMep150, with the composition | (C5N2H14)3(H2O)10 | [Al6P8O32(H2O)2], crystallized at 150 °C in the form of large hexagonal prisms in space group P3 (no. 143) with a=13.240(14) Å and c=9.672(5) Å. The aluminophosphate layer consists of a network of 4-, 6- and 12-membered rings. This type of layer is observed in other layered aluminophosphates, but differs here by the presence of a disordered aluminum octahedron in the unit cell. The structure contains a one-dimensional channel system along the [0 0 1] direction, generated by the alignment of the 12-rings units. These channels contain water molecules and are partially occluded by the methyl groups of 2-methylpiperazinium ions. Water molecules can be reversibly removed at moderate temperature without significant modifications of the unit cell parameters. The dehydrated compound, which contains only AlO4 and PO4 tetrahedra and the organic template, possesses channels with a window size of ≈4.0×6.6 Å. The other layered compound, named APMeP200, has been obtained at 200 °C and its structure is almost identical to that of AP2pip, a compound synthesized in the presence of piperazine. APMeP200 has the composition | (C5N2H14)4.5(H2O)2.5 | [Al9P12O48], and crystallizes in space group P21/c (no. 14) with a=22.12(3) Å, b=19.09(2) Å, c=16.541(16) Å and β=99.96(9). The structure can accommodate the extra methyl groups without significant modifications of the unit cell, because these groups displace some of the water molecules present in AP2pip.

Synthesis, characterization and structure determination of two novel layered aluminophosphates templated by 2-methylpiperazine