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NMR crystallography to probe the breathing effect of the MIL‐53(Al) metal–organic framework using solid‐state NMR measurements of 13 C– 27 Al distances
Author(s) -
Giovine Raynald,
Volkringer Christophe,
Trébosc Julien,
Amoureux Jean-Paul,
Loiseau Thierry,
Lafon Olivier,
Pourpoint Frédérique
Publication year - 2017
Publication title -
acta crystallographica section c
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.304
H-Index - 17
ISSN - 2053-2296
DOI - 10.1107/s2053229616017915
Subject(s) - solid state nuclear magnetic resonance , dephasing , carbon 13 nmr , chemistry , crystallography , nuclear magnetic resonance , materials science , analytical chemistry (journal) , condensed matter physics , physics , stereochemistry , chromatography
The metal–organic framework MIL‐53(Al) (aluminium terephthalate) exhibits a structural transition between two porous structures with large pore ( lp ) or narrow pore ( np ) configurations. This transition, called the breathing effect, is observed upon changes in temperature or external pressure, as well as with the adsorption of guest molecules, such as H 2 O, within the pores. We show here how these different pore openings can be detected by observing the dephasing of 13 C magnetization under 13 C– 27 Al dipolar couplings using Rotational‐Echo Saturation‐Pulse Double‐Resonance (RESPDOR) solid‐state NMR experiments with Simultaneous Frequency and Amplitude Modulation (SFAM) recoupling. These double‐resonance NMR experiments between 13 C and 27 Al nuclei, which have close Larmor frequencies, are feasible thanks to the use of a frequency splitter. The experimental SFAM–RESPDOR signal fractions agree well with those simulated from the MIL‐53(Al)‐ lp and ‐ np crystal structures obtained from powder X‐ray diffraction analysis. Hence, these 13 C– 27 Al solid‐state NMR experiments validate these structures and confirm their rigidity. A similar agreement is reported for the framework ligands in the as‐synthesized ( as ) MIL‐53(Al), in which the pores contain free ligands. Furthermore, in this case, 13 C–{ 27 Al} SFAM–RESPDOR experiments allow an estimation of the average distance between the free ligands and the 27 Al nuclei of the framework.