Events Calendar

Brancoft Award Lecture-Vinicius dos Santos, Ph.D. Candidate

Wednesday, November 11, 2020
1:30 pm - 2:30 pm
Room: via ZOOM

Vinicius dos Santos (Ph.D Candidate)
Department of Chemistry
Western University

will present a talk entitled:

"17O solid-state NMR at 35.2 T: Ultrahigh spectral resolution unlocks ultrafine information on oxygen environments in MOFs"

Metal−organic frameworks (MOFs) are a class of porous materials that have shown great promise for many important applications. MOF characterization is crucial to understanding the structure-property relation. Many important MOFs contain various oxygen species and they play important roles in many applications. Therefore, understanding the local environment of oxygen can provide valuable structural information. 17O solid-state NMR (SSNMR) is an ideal technique for characterization. However, 17O is a challenging nucleus to study via SSNMR, as it suffers from low sensitivity and resolution due to the quadrupolar interaction and low 17O natural abundance.

Recently, we have demonstrated that ultrahigh 17O spectral resolution can be achieved at an ultrahigh magnetic field of 35.2 T. We were able to unlock complete identification of all twelve inequivalent carboxylate oxygen sites in as-made and activated phases of MOF(alpha)-Mg3(HCOO)6. The subtle 17O spectral differences between the as-made and activated phases yield fine information about host−guest interactions, including insight into nonconventional O∙∙∙H−C hydrogen bonding. Such weak interactions often play key roles in applications of MOFs, such as gas adsorption and biomedicine, and are usually difficult to study via other characterization routes. We have also investigated the phase transitions in MOF MIL-53(Al). By using 17O isotopic enrichment and performing 17O SSNMR experiments at an ultrahigh magnetic field of 35.2 T, all chemically and crystallographically inequivalent oxygen sites in three representative MIL-53(Al) (as-made, activated and water adsorbed) phases can be completely resolved. The number of peaks in each phase is consistent with that predicted from the space group refined from powder X-ray diffraction data. The 17O 1D Magic-Angle Spinning (MAS) and 2D 3QMAS spectra at 35.2 T furnish key information about the host-guest interactions and the structural changes associated with phase transition.

Department of Chemistry
Yining Huang - Supervisor
Event Type:

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