Dynamic Nuclear Polarization Enhanced Natural Abundance ¹⁷O Spectroscopy

We show that natural abundance oxygen-17 NMR of solids could be obtained in minutes at a moderate magnetic field strength by using dynamic nuclear polarization (DNP). Electron spin polarization could be transferred either directly to ¹⁷O spins or indirectly via ¹H spins in inorganic oxides and hydroxides using an oxygen-free solution containing a biradical polarization agent (bTbK). The results open up a powerful method for rapidly acquiring high signal-to-noise ratio solid-state NMR spectra of ¹⁷O nuclear spins and to probe sites on or near the surface, without the need for isotope labeling

Dynamic Nuclear Polarization NMR Spectroscopy Allows High-Throughput Characterization of Microporous Organic Polymers

Dynamic nuclear polarization (DNP) solid-state NMR was used to obtain natural abundance ¹³C and ¹⁵N CP MAS NMR spectra of microporous organic polymers with excellent signal-to-noise ratio, allowing for unprecedented details in the molecular structure to be determined for these complex polymer networks. Sensitivity enhancements larger than 10 were obtained with bis-nitroxide radical at 14.1 T and low temperature (∼105 K). This DNP MAS NMR approach allows efficient, high-throughput characterization of libraries of porous polymers prepared by combinatorial chemistry methods