Phase transition and molecular motion of cyclohexane confined in metal-organic framework, IRMOF-1, as studied by 2H NMR

Molecular motion and thermal properties of cyclohexane confined in [Zn4O(O2CC6H4CO2)3]n (IRMOF-1) were examined using 2H NMR and differential thermal analysis (DTA) measurements. DTA measurement revealed that cyclohexane confined in IRMOF-1 exhibits thermal anomaly at 121 K, 213 K and 306 K. Subsequent 2H NMR elucidated that cyclohexane undergoes precession of the C3-axis at temperatures below 120 K and shows a tumbling motion with the large amplitude fluctuation of the precession axis from 120 K to 200 K; then isotropic reorientation is excited at temperatures above 200 K, revealing that cyclohexane in IRMOF-1 melts at 213 K.