A solid-state NMR study of the molecular sieve VPI-5 synthesized in the presence of a CTABr surfactant.

Silicon-free and silicon-rich large-pore aluminophosphate VPI-5, synthesized with various contents of AIPO-H3 impurity, was studied by Bloch decay (BD) and cross polarization (CP) NMR under magic angle spinning (MAS). The 1H-->31P CP peaks were considerably stronger from AIPO-H3 than from VPI-5. A detailed examination of the CP kinetics and a careful comparison of the CP and BD spectra are prerequisites for the unequivocal interpretation of 1H-->31P CP in porous aluminophosphates.