Double-resonance decoupling for resolution enhancement of 31P solid-state MAS and 27Al --> 31P MQHETCOR NMR.

27Al decoupling has been used to remove residual J-coupling interactions between 31P and 27Al in microporous aluminophosphates AlPO4-14 and AlPO4-40. In combination with 1H high-power decoupling, 27Al adapted decoupling yields 31P spectra with optimal sensitivity and resolution. The importance of double-resonance decoupling is further demonstrated by incorporating this technique in the MQHETCOR sequence. Unambiguous assignment of all the AlPO4-14 nuclear magnetic resonances is achieved by combining multiple-quantum evolution in the 27Al dimension and double-resonance decoupling in the 31P acquisition domain.