129Xe Nuclear Magnetic Resonance Spectroscopy of Metal–Organic Frameworks

Abstract

¹²⁹Xe nuclear magnetic resonance (NMR) spectroscopy is a powerful tool for the investigation of various porous materials, for example, zeolites, metal–organic frameworks (MOFs), and covalent organic frameworks. Structure determination of MOFs usually relies on diffraction methods. NMR spectroscopy is complementary to the long-range information provided by diffraction techniques since it relies on the exploitation of short-range interactions without the need for long-range order. This allows, for example, the study of interactions of MOFs with guest atoms as well as structural transitions initiated by adsorbed molecules. For such purposes, ¹²⁹Xe is a well-suited, inert NMR probe atom that sensitively reflects host–guest interactions. This is due to its high sensitivity to alterations in its close environment, e.g., interactions caused by xenon adsorption inside the cavities of a porous material. The present review introduces the basic properties and possibilities of ¹²⁹Xe NMR in porous materials and is focused on recent achievements in the field of metal–organic frameworks. Different experimental techniques, including their respective possibilities and limitations, as well as their application to specific research questions like framework flexibility and adsorption selectivity, are presented.