Chemically nonequivalent sites in mesoporous BCN revealed by solid-state NMR at 21.8 T

Solid-state B-11 magic-angle spinning (MAS) NMR studies on novel mesoporous BCN material are described. While the B-11 MAS spectrum at 11.7 T shows severe signal overlap as a result of the second-order quadrupolar broadening, the resolution improves significantly at 21.8 T and three distinct peaks are observed, indicating the presence of three sites in the material. Possible microstructures of the three sites are discussed in terms of their isotropic chemical shifts, quadrupolar coupling constants, and asymmetric parameters determined from spectral simulation.