PORE-RESOLVED NMR POROSIMETRY

For the first time, high-field FT-NMR spectra of an adsorbate inside a porous solid exhibits multiple resonances corresponding to different sites. Frequency shift, T-1, and T-2 measurements as a function of adsorbate concentration support the assignment of these resonances to probe molecules in solution and in pores of various sizes within the solid. Resolution of the bands and combination of the NMR intensities with the adsorption isotherm lead to an unprecedented amount of detail about the distribution of the adsorbate in the solid pores as a function of probe concentration (see Figures 5 and 6). The detection of separate resonances by NMR is referred to as pore-resolved NMR porosimetry to distinguish this method from NMR analyses based on extracting information from a single resonance of an adsorbed probe molecule.