The 11 B MAS NMR experiments were conducted with a pulse width of 0.33 µs and a 15-kHz spinning speed. The recycle delays for complete relaxation and signal accumulation were 30 s and 64, respectively. The reference for the chemical shifts was a 1.0-M aqueous solution of H 3 BO 3 at 19.5 ppm. Spectral simulations of the 11 B MAS NMR spectra were conducted using an in-house program incorporating the mrsimulator Python package. Results and discussion