Investigation of molecular motion of Cl-adamantane in the nanoprous zeolite by 13C NMR dipolar dephasing and variable contact time measurements

Abstract

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 ¹³C NMR spectroscopy and dipolar dephasing technique were applied to determine the extent of motion <em>1</em><em>-</em><em>Chloroadamantane</em>loaded in nonporouszeolite-Y. Loading of <em>1</em><em>-</em><em>Chloroadamantane</em> into the supercages of the zeolite-Y (with R=100 and R=2.35, 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 <em>1</em><em>-</em><em>Chloroadamantane</em>to determine the degree of motion in the nonporousof zeolite-Y. Results indicated that the C_d signal of the <em>1</em><em>-</em><em>Chloroadamantane</em>in the nonporous zeolite-Y decays faster than that the C_b and C_g, demonstrating that dipolar interaction for this carbon (C_d) is stronger. However, the rate of signal decay C_d for the <em>1</em><em>-</em><em>Chloroadamantane</em>loaded in zeolite -Y (R=2.35) is less than that loaded in zeolite-Y (R=100).