CHARACTERIZATIONS OF MAPO-36 MOLECULAR-SIEVE BY SOLID-STATE NMR

The structure of the MAPO-36 framework was studied by the Al-21 and P-31 magic angle spinning (MAS) n.m.r. technique. The change in the Al-27 chemical shift from the tetrahedral aluminum position to the octahedral aluminum position upon adsorption of water indicates a secondary coordination of water molecules to aluminum atoms in the framework. The spectral change was reversible. The P-31 MAS n.m.r. spectra also changed reversibly upon adsorption and desorption of water. A strong interaction of water molecules and phosphorus atoms was confirmed by a large enhancement of the signal by [H-1-P-31] cross-polarization (CP) mode.