Solid-state nuclear magnetic resonance (SSNMR) spectroscopy of materials is undergoing a rapid expansion due to the development of high-field dynamic nuclear polarization (DNP), a technique yielding sensitivity improvements of 2-3 orders of magnitude. In particular, the DNP-driven hyperpolarization of nuclear spins opens an unprecedented range of opportunities in catalysis by enabling studies of much smaller surface areas than previously possible and/or examination of highly dispersed surface species. We will highlight some of these new opportunities, focusing mainly on DNP-enhanced two-dimensional homo- and hetero-nuclear correlation (HETCOR) NMR spectroscopy. The applications will include the 1H-15N and 1H-13C HETCOR spectra of natural abundance catalytic moieties, which will be compared with the conventional state-of-the-art HETCOR measurements utilizing magic angle spinning at rates up to 100 kHz. The first natural abundance 17O DNP NMR spectra of surface silanol groups will be presented, in which the hyperpolarized 1H magnetization was efficiently transferred to 17O using the PRESTO technique. The PRESTO approach can be easily altered to measure 1H-17O HETCOR spectra and 1H-17O internuclear distances. This has enabled the detection of hydrogen-bonded and non-hydrogen-bonded silanol groups at the surface of silica gel, which cannot be distinguished otherwise. We will also present the DNP-enhanced spectra of other challenging systems, including 27Al{1H} and 29Si(1H} CPMAS spectra small-surface surfaces, and 13C-13C spectra of molecules reacting on surfaces of metal nanoparticles.

Characterization of amorphous catalytic materials by DNP-enhanced solid-state NMR methods

251st National Meeting (2016)

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