Functional group resolved NMR relaxation of 3-carbon adsorbates in mesoporous alumina

NMR relaxation analysis provides a unique and non-invasive probe of fluid dynamics within porous materials, and may be applied to the interpretation of a wide variety of material and interfacial characteristics. Here, we report two-dimensional ¹H $T_1-T_2$ relaxation correlation measurements of a range of three-carbon adsorbates (1-propanol, 2-propanol and propanoic acid) imbibed within the mesoporous metal oxide gamma-alumina. Our data, acquired across field strengths of 2 MHz, 12.7 MHz and 43 MHz, clearly reveal two populations in each measurement, identified as the alkyl and hydroxyl moieties of each adsorbate. These results expand the range of materials in which such functional group resolved relaxation is known to occur, and demonstrate the clear persistence of such phenomena using a range of typical benchtop NMR systems employed to study fluid-saturated porous media.