Probing Metal Organic Frameworks with 17O NMR at 35.2 T

Published October 16, 2020

The α-Mg3(HCOO)6 metal-organic framework that contains twelve unique oxygen sites.

Metal-organic frameworks (MOFs) are porous materials with high surface areas that can host a variety of different guest molecules, leading to applications in catalysis, drug delivery, chemical separation, fuel cells, and data storage. In order to design better MOFs, knowledge of their molecular-level structures is crucial. At the MagLab, the highest-field NMR spectrometer in the world was used to probe the complex structures of MOFs both "as built" and as they exist when other "guest" molecules are inserted inside the framework.

What did scientists discover?

Using the highest-field nuclear magnetic resonance (NMR) spectrometer in the world, researchers were able to resolve 12 distinct oxygen sites in the structure of a complex metal-organic framework (MOF) and observe differences in the structures of MOFs that either contain guest molecules or are free from guest molecules.

Why is this important?

In order to design better MOFs for use in catalysis, drug delivery, chemical separation, gas adsorption, fuel cells, and/or data storage, scientists must have a precise understanding of their structures. This helps in the design and manufacture of new MOFs from very simple chemicals, and also for tailoring and controlling the properties of MOFs for a wide range of applications.

Who did the research?

V. Martins¹, J. Xu², X. Wang³, K. Chen³, I. Hung v³, Z. Gan³, C. Gervais⁴, C. Bonhomme⁴, S. Jiang⁵, A. Zheng⁵, B. Lucier¹, Y. Huang¹

¹Western University, London, ON, Canada; ²Nankai University, Tianjin, China; ³National MagLab, Tallahassee FL, USA; ⁴Sorbonne University, Paris, France; ⁵Chinese Academy of Sciences, Wuhan, China

Why did they need the MagLab?

The NMR spectrometer magnet used for this work, the MagLab's 35.2 Tesla Series-Connected Hybrid (SCH) magnet, is the largest NMR magnet in the world, and is the only one capable of obtaining high enough signal and resolution to enable observation of all of the different oxygen sites. The 17O isotope is challenging to observe with lower field instruments, which cannot provide this high degree of information. The SCH will be critical for many future 17O NMR studies, as well as studies of elements from across the periodic table in MOFs and other technologically-advanced materials.