17O Labeling Reveals Paired Active Sites in Zeolite Catalysts

Published November 14, 2022

Left: A zeolite micropore and pair of active sites. Right: The signal-to-noise and spectral resolution in 17O NMR spectra is significantly enhanced at higher magnetic fields.

Zeolite catalysts are critical to generating the molecules that provide the building blocks of society’s energy and materials needs. Discerning a clear atomic-level picture of the active sites remains challenging for most current technologies, but here we show that solid-state nuclear magnetic resonance (ssNMR) methods coupled with ultra-high magnetic field instruments, can and has provided extremely useful information for catalyst development.

What did scientists discover?

Crucial details on the structures and proximities of active catalytic sites in zeolite catalysts are revealed by ultra-high-magnetic-field solid-state nuclear magnetic resonance (ssNMR) methods that include enrichment of the catalyst by ¹⁷O isotopic substitution.

Why is this important?

Zeolite catalysts are widely used in modern industrial processes, such as petrochemical refinement and biomass conversion. Economic, environmental, and engineering requirements dictate that fundamental understanding of structure and performance drive new catalyst developments. Recent studies show that active catalytic sites are more complex than previously thought. A phenomenon of great importance is the synergistic effect, where the reactivity of two proximate (nearby) active sites is increased relative to that of two sites separated by a large distance. Ultra-high-magnetic-field ¹⁷O ssNMR experiments conducted on a variety of catalyst samples enriched with ¹⁷O isotopes revealed potential synergistic site structures. Such information is crucial for the rational design, synthesis, and manufacture of catalysts with improved efficiency and yields.

Who did the research?

Kuizhi Chen,¹ Anya Zornes,² Vy Nguyen,³ Bin Wang,³ Zhehong Gan,¹ Steven P. Crossley, and Jeffery L. White²

¹National MagLab; ²Oklahoma State University; ³University of Oklahoma

Why did they need the MagLab?

Ultra-high-magnetic-field (UHMF) ssNMR spectroscopy of ²⁷Al and ¹⁷O nuclei provides structural details that cannot be obtained from experiments at lower fields, offering an unprecedented combination of high signal and high resolution that is required for these observations. This is made possible by the combination of UHMF ssNMR platforms and state-of-the-art probes available only at the MagLab.