Higher Magnetic Fields, Finer MOF Structural Information: 17 O Solid-State NMR at 35.2 T

作者：Vinícius Martins, Jun Xu, Xiao-Ling Wang, Kuizhi Chen, Ivan Hung, Zhehong Gan, Christel Gervais, Christian Bonhomme, Shijia Jiang, Anmin Zheng, Bryan E. G. Lucier, Yining Huang · 发表于：Journal of the American Chemical Society · 年份：2020 · DOI：10.1021/jacs.0c02810 · 被引用次数：70 · 研究领域：Advanced NMR Techniques and Applications、Metal-Organic Frameworks: Synthesis and Applications、Crystal Structures and Properties

The spectroscopic study of oxygen, a vital element in materials, physical, and life sciences, is of tremendous fundamental and practical importance. 17 O solid-state NMR (SSNMR) spectroscopy has evolved into an ideal site-specific characterization tool, furnishing valuable information on the local geometric and bonding environments about chemically distinct and, in some favorable cases, crystallographically inequivalent oxygen sites. However, 17 O is a challenging nucleus to study via SSNMR, as it suffers from low sensitivity and resolution, owing to the quadrupolar interaction and low 17 O natural abundance. Herein, we report a significant advance in 17 O SSNMR spectroscopy. 17 O isotopic enrichment and the use of an ultrahigh 35.2 T magnetic field have unlocked the identification of many inequivalent carboxylate oxygen sites in the as-made and activated phases of the metal–organic framework (MOF) α-Mg 3 (HCOO) 6 . The subtle 17 O spectral differences between the as-made and activated phases yield detailed information about host–guest interactions, including insight into nonconventional O···H–C hydrogen bonding. Such weak interactions often play key roles in the applications of MOFs, such as gas adsorption and biomedicine, and are usually difficult to study via other characterization routes. The power of performing 17 O SSNMR experiments at an ultrahigh magnetic field of 35.2 T for MOF characterization is further demonstrated by examining activation of the MIL-53(Al) MOF. Th...