Fig. 3. 17O (14.1 T, 20 kHz) (a, b) spin echo MAS and (c, d) MQMAS NMR spectra of calcined, hydrated (a, c) Al MIL-53 and (b, d) Ga MIL-53. In (c, d), only the carboxylate region of the spectrum is shown. (e) Possible hydrogen-bonding arrangements in hydrated MIL-53 (M = Al, Ga) based on DFT-optimised literature59 structures. See ESI for more detail.† .
