. The REDOR difference spectrum (DS) between the spectrum
with 31P pulses switched off (S) and switched on (S0) clearly
showed that for both TPE-S/AlPi/MH (Fig. 11a) and TPE-S/AlPi/ZB/
PPO (Fig. 11b) signals at 40 ppm were coming from aluminates
that have phosphorus nearby.