Mu-7, a new layered aluminophosphate [CH3NH3](3)[Al3P4O16] with a 4 x 8 network: Characterization, structure, and possible crystallization mechanism

The title compound, Mu-7, is a new layered aluminophosphate. It was obtaine d from a quasi-nonaqueous system involving methylformamide (MF) as solvent in addition to restricted amounts of water. MF is decomposed into methylami ne during synthesis and the latter is occluded into the interlayer spacing of the material. The structure was determined by single-crystal X-ray diffr action. The symmetry is triclinic, space group P (1) over bar, a = 8.368(7) , b = 11.274(10), c = 11.462(12) Angstrom, alpha = 72.40(7), beta = 89.45(8 ), and gamma = 85.37(7)degrees. Mu-7 is built from zigzag ladder-type chain s connected to form layers containing only four- and eight-membered rings. Mu-7 is the first lamellar aluminophosphate having such a 4 x 8 network. Ch aracterization of the new compound by C-13, Al-27, and P-31 solid-state NMR spectroscopy, bulk chemical analysis and TG/DSC is reported. A possible cr ystallization mechanism based on the condensation between "parent" ([AlP2O8 H2](-)) and zigzag ladder-type ([Al4P4O20H4](4-)) chains is proposed.