Multifield magic-angle spinning and double-rotation nuclear magnetic resonance studies of a hydrated aluminophosphate molecular sieve: AlPO 4-H2

Abstract

AlPO 4-H2 is a microporous hydrated aluminophosphate, structurally related to VPI-5, whose framework has highly elliptical 10-ring channels (2.9 × 7.6 Å) parallel to the c crystallographic axis. To resolve a previously reported discrepancy between nuclear magnetic resonance (NMR) and X-ray diffraction (XRD) data a highly crystalline AlPO 4-H2 has been further characterized with 27Al and 31P magic-angle spinning (MAS) NMR at 11.7 T and 27Al double-rotation (DOR) NMR at 4.7 T. These present NMR data definitively show that the true space group symmetry of the AlPO 4-H2 framework structure is triclinic rather than the higher orthorhombic symmetry proposed earlier from XRD studies.