Determination of the location of naphthalene in the zeolite ZSM-5 host framework by solid-state H-1/Si-29 CP MAS NMR spectroscopy

The location of naphthalene in the zeolite ZSM-5 has been determined from solid-state H-1/Si-29 cross-polarization (CP) magic-angle-spinning (MAS) NMR data alone. With the peaks in the Si-29 spectrum assigned to the inequivalent Si sites in the zeolite from a two-dimensional INADEQUATE spectrum, the rates of cross polarization between the H-1 nuclei of the guest sorbate molecules and the Si-29 nuclei of the zeolite framework were used to determine the location of the naphthalene molecules by exploiting the proportional relationship between cross-polarization rate constants and H-1/Si-29 dipolar coupling second moments. The NMR structure determination was carried out on three different selectively deuterium-labeled naphthalene molecules (naphthalene-d(0), alpha-naphthalene-d(4), and beta-naphthalene-d(4)). The average of the molecule locations in agreement with all three sets of NMR data was found to be in excellent agreement with an existing single crystal XRD structure of the naphthalene-ZSM-5 complex.