A convenient one-dimensional magic-angle spinning NMR method is presented that provides selective NMR spectra of COH moieties in uniformly 13C-enriched organic materials. This method, termed hydroxyl-proton selection (HOPS), eliminates the magnetization of protons directly bonded to carbons by recoupling the 1H-13C dipolar interaction for a short time (∼70 μs), which also serves as a chemical-shift filter to suppress 1H magnetization of CH3 groups. After cross polarization to 13C, the signals of COH and COOH carbons are observed selectively. This makes it possible to distinguish alcohols from ethers, in particular phenols from aromatic ethers such as the furans often formed by dehydration of glucose, and carboxylic acids from carboxylates and ethers. HOPS NMR reveals that orthodiphenols are often a major component of low-temperature carbon materials. For instance, it forces the reassignment of the 143 ppm 13C NMR signal of hydrothermal carbon to such catecholic diphenols, while a previous NMR-based structural model had attributed this peak to a central furan-furan linkage.