The 1 H and Al MAS ssNMR spectra were acquired in 3.2 mm ZrO 2 rotors on a Bruker Avance NEO 700 MHz spectrometer with a PH MASDVT700S3 BL3.2 N-P/F-H probehead at 298 K. The samples were packed into the rotors in a drybox, sealed and stored under the inert atmosphere of the drybox until measurement. The 1 H spectra were obtained using standard 90°-pulse excitation at 20 kHz MAS frequency with 8 s delays and 1 H chemical shifts referenced to crystalline alanine (δ = 1.2 ppm, CH3 signal).