Controllable synthesis of Co-MOF-74 catalysts and their application in catalytic oxidation of toluene

The morphology and size of Co-MOF-74 were effectively controlled by adjusting the water portion in DMF-H₂O mixed solvent system, and six different Co-MOF-74 samples were successfully obtained. The water content can alter the deprotonation rate of the organic ligand and then change the nucleation rate of crystal, thus regulate morphology and size of Co-MOF-74. The discrepancy of morphology and size has significant effect on texture structure of Co-MOF-74 but without changing their composition. The formation mechanism of crystal growth was proposed by studying the change of reaction solution pH value. These samples exhibit morphology and size dependent catalytic activity in toluene oxidation. The flower-like sample has the best catalytic performance with 12.1% toluene conversion and 63.8% benzaldehyde selectivity. Additionally, the influence of reaction parameters on the catalytic oxidation reaction was also examined. Rearserch on the structure-property relationship of catalyst would be useful for rationally synthesizing novel MOF in heterogeneous catalysis.