Selective oxidation of glycerol to lactic acid catalyzed by Cu-based MOFs

The researchers synthesized four copper-based MOFs (Cu-MOF, Cu-MOF-74, Cu-PTA-MOF, and NH₂-Cu-MOF) and used them for the first time in the selective catalytic oxidation of glycerol to lactic acid. The crystal phase, morphology, crystal structure and chemical state of surface elements of the catalysts were characterized by XRD, SEM, TEM and XPS. The results show that the active sites of Cu-based MOFs are all Cu²⁺. Cu-MOF has the largest specific surface area and the smallest lattice spacing. From this, it can be seen that Cu-MOF has the most active catalytic sites, promotes charge transfer and increases electron mobility, effectively improving glycerol adsorption capacity. The Cu-MOF with spherical morphology has the strongest catalytic ability. Glycerol conversion is as high as 97.15 %, and the lactic acid selectivity is 82.02 %. The adsorption properties of glycerol on the surface of Cu-based MOFs were studied by density functional theory (DFT) calculations. The results show that Cu-MOF has the largest adsorption energy, which is favorable for the bonding of glycerol on its surface. Cycling experiments demonstrated that Cu-MOF showed good stability during the catalytic process and no significant changes in the crystalline phase and valence state of the reacted Cu-MOF were observed by XRD and XPS.