Al-27/P-31 solid-state nmr structural investigations of AlPO4-5 molecular sieve

Al-27/P-31 solid-state n.m.r. connectivity experiments were used to investigate the structure of the molecular sieve AlPO4-5 hydrated with D2O. Hydration with D2O resulted in an increased efficiency of coherence transfer from octahedral Al-27 to P-31 compared with hydration with H2O. The experiments prove directly that both the tetrahedral aluminum and the octahedral aluminum formed upon hydration are connected to phosphorus in the framework. The two-dimensional Al-27 –> P-31 transferred-echo double-resonance and cross-polarization experiments show a downfield offset of the octahedral Al-27 correlation from the tetrahedral Al-27 correlation, consistent with the growth of a downfield shoulder on the P-31 resonance as water is incorporated into the lattice.