Investigation of molecular motion of Cl-adamantane in the nanoprous zeolite by ۱۳C NMR dipolar dephasing and variable contact time measurements

Dipolar-dephasing method provides some information about the strength of dipolar coupling in solids. Dipolar dephasing technique measures the time for a polarized carbon nucleus to lose its magnetization once the proton locking field is terminated. The dynamics of guest molecules adsorbed within the cavities and channels of nonporouszeolite strongly depend on the structure and chemical composition of the nonporouszeolite. In this work solid-state ۱۳C NMR spectroscopy and dipolar dephasing technique were applied to determine the extent of motion ۱-Chloroadamantaneloaded in nonporouszeolite-Y. Loading of ۱-Chloroadamantane into the supercages of the zeolite-Y (with R=۱۰۰ and R=۲.۳۵, R=Si/Al) was carried out by a vapor phase impregnationand solution impregnation methods. The accuracy of dipolar dephasing method was first investigated with the aid of pure ۱-Chloroadamantaneto determine the degree of motion in the nonporousof zeolite-Y. Results indicated that the Cd signal of the ۱-Chloroadamantanein the nonporous zeolite-Y decays faster than that the Cb and Cg, demonstrating that dipolar interaction for this carbon (Cd) is stronger. However, the rate of signal decay Cd for the ۱-Chloroadamantaneloaded in zeolite -Y (R=۲.۳۵) is less than that loaded in zeolite-Y (R=۱۰۰). 

Keywords:

۱-Chloroadamantane , CPMAS NMR , Dipolar dephasing , Impregnation , Molecular motion , Nonporous , Zeolite-Y