Pore structure of mordenite was probed by ¹H and ¹⁹F NMR spin-lattice relaxation times of guest molecules adsorbed. Small molecules such as CH₄ and CF₄ could be adsorbed in mordenite, and shows molecular motions, which are very sensitive to the interaction between the molecules and the pore wall of mordenite.  Therefore, the structure and potential energy of pore could be probed by the measurements of ¹H and ¹⁹F NMR spin-lattice relaxation times of molecules adsorbed.