“…Instead, there is considerable interest in developing proton-based solid-state NMR spectroscopy that fully utilizes the high sensitivity of protons afforded by its highest gyromagnetic ratio and nearly 100% natural abundance. − Fortunately, by virtue of the tremendous advances in magic angle spinning (MAS) probe technologies, spinning can be up to 170 kHz now using a small rotor with a diameter of less than 0.5 mm, , and the probe with the capability of spinning beyond 60 kHz has indeed become common in many NMR laboratories. Under such fast MAS conditions, the strong proton–proton dipolar couplings can be significantly averaged, leading to a dramatic enhancement of proton spectral resolution particularly when combined with an ultrahigh magnetic field. − Indeed, we have previously fully exploited multidimensional single channel proton solid-state NMR experiments at fast MAS conditions in order to fully explore the benefits of high sensitivity of protons for structural analysis of minute amounts of organic solids. − Particularly, homonuclear 1 H/ 1 H single-quantum/single-quantum (SQ/SQ) and double-quantum/single-quantum (DQ/SQ) correlation experiments are widely adapted for probing the proximity of protons, enabling revealing the hydrogen bonding interactions, intermolecular compatibility, and chain packings. − Nevertheless, it should be noted that the spectral resolution of proton is not comparable to that of 13 C spectra, and a proton-detected 13 C/ 1 H heteronuclear correlation (HETCOR) experiment is typically required for accurate proton resonance assignments and thus enabling rapid structural analysis. − Notably, in the conventional proton-detected HETCOR experiment (Figure a), , only around 1% of 1 H polarization is transferred to 13 C via the first cross-polarization (CP) period for the natural abundance organic solids since the natural abundance of 13 C is only around 1%, while 99% of 1 H polarization is actually destroyed and wasted by the heteronuclear decoupling or homonuclear rotary resonance (HORROR) period to fully eliminate the residual proton polarization before second CP transfer for proton detection. In the previous study, we have well demonstrated that those residual 99% 1 H polarization can be further utilized for subsequent multiple CP polarization transfer at fast MAS conditions if the proton T 1ρ is long enough, even enabling the direct acquisition of natural abundant 13 C NMR spectra using only ∼2 mg compounds .…”