Structure distortion of Zn4O13C24H12 framework (MOF-5)

Zn4O13C24H12 framework (MOF-5) can occupy either cubic or tetragonal structure. It was recognized that the tetragonal MOF-5 was a distorted cubic MOF-5 caused by filling effect of ZnO or solvent. However, herein, it was found that the ZnO and solvent inside the pores of the framework did not cause the distortion of cubic MOF-5. Furthermore, the distortion is strongly dependent on the solvent vacuumed to dry the framework. If the vacuumed solvent was dimethylformamide (DMF), the crystal structure of MOF-5 was tetragonal. In contrast, if DMF was displaced by CH2Cl2 before the vacuum, the obtained MOF-5 occupied a perfect cubic structure. The thermal decomposition of cubic and tetragonal MOF-5s produced the same products: CO2, benzene, amorphous carbon, and crystal ZnO. However, the thermal decomposition of cubic MOF-5 requires a higher temperature than the tetragonal one, indicating that cubic MOF-5 is more stable than the tetragonal one.