Deuterium NMR studies of framework and guest mobility in the metal–organic framework compound MOF-5, Zn4O(O2CC6H4CO2)3

Abstract Variable temperature wideline 2 H NMR investigations of the mobility of aromatic rings in the framework of desolvated samples of the metal organic framework compound MOF-5 (Zn 4 O(O 2 CC 6 H 4 CO 2 ) 3 ) and the closely related solid MOCP-L have been performed. The aromatic rings in MOF-5 are stationary at temperatures lower than room temperature but perform 180° ( π ) flips at higher temperatures until all framework aromatic groups execute this motion at 373 K. The aromatic groups in MOCP-L demonstrate a higher degree of mobility with some motion even below 170 K. 2 H NMR of perdeuterobenzene adsorbed onto MOF-5 at a loading of two molecules per Zn 4 O 13 inorganic unit shows that upon cooling below 140 K the motion of benzene changes from isotropic reorientation to rotation about its six-fold axis. Computational simulation suggests that benzene occupies a site close to the Zn 4 O 13 unit at low temperatures.