Synthesis and structure of Mu-10:: a novel microporous hydroxyaluminophosphate (CH3)2NH2•Al3P3O12OH closely related to AlPO4-EN3

A new hydroxyaluminophosphate (CH3)(2)NH2. Al3P3O12OH called Mu-10 was obtained by hydrothermal synthesis from an Al2O3/P2O5/ dimethylamine mixture in aqueous medium. The structure was determined by single crystal X-ray diffraction. Mu-10 crystallizes in an orthorhombic symmetry, space group Pbca (No.61) with a = 13.678 (2) Angstrom, b = 10.318 (3) Angstrom, c = 17.357 (3) Angstrom, V = 2449.6 Angstrom(3) and Z = 8. The unit cell contains 3 symmetrically independent [PO4] tetrahedra, 2 types of trigonal-bipyramids [AlO4(OH)] and one type of [AlO4] tetrahedra. These polyhedra are linked by their oxygen atoms with pairs of adjacent Al atoms in fivefold coordination sharing a common hydroxyl group. When omitting the OH groups, the three-dimensional framework can be described as an assembly of layers extending parallel to the a-c plane and consisting of 4-,6- and 8- membered rings. Stacking the layers along the [010] direction in an ABAB... sequence generates a system of interconnected zig-zag channels limited by 8-ring apertures. Neighboring layers are shifted relative to each other by a vector of 0.375xa in the [100] direction. The topology of the Mu-10 framework is identical to that of AlPO4-EN3, the two materials, however, are different with respect to symmetry and chemical composition. The negative charge of the framework is compensated by the protonated dimethylamine which is occluded in the channels. The structure determination was confirmed by C-13, Al-27 and P-31 solid state NMR spectroscopy.