NATURAL ABUNDANCE, 2-DIMENSIONAL SI-29 MAS NMR INVESTIGATION OF THE 3-DIMENSIONAL BONDING CONNECTIVITIES IN THE HIGH-TEMPERATURE AND LOW-TEMPERATURE FORMS OF ZEOLITE ZSM-11

Two-dimensional 29Si solid-state NMR experiments have been used to investigate the three-dimensional bonding connectivities in ZSM-11 in both its high- and low-temperature forms, which are related to each other by a temperature-induced phase transition. The high-temperature form is known to have tetragonal symmetry with space group I4BARm2, while the details of the ZSM-11 structure at low temperatures are not known to date from diffraction measurements. 2-D INADEQUATE experiments at high temperature (340 K) confirmed the postulated structure. All of the nine expected connectivities were observed, permitting an unambiguous assignment of the spectrum. In the low-temperature (303 K) 2-D experiments, enough information was obtained that, combined with the knowledge of the high-temperature structure, a structure could be suggested for the low-temperature form. The complete connectivities of T sites in the structure were established, and at least one space group, I4BAR, is compatible with the NMR data.