Catalytic Oxidation Of Cyclohexene And Styrene Over Cu And Co-Containing Metal-Organic Frameworks

The catalytic oxidation of alkenes into value-added oxygenated derivatives is a fundamental reaction in organic chemistry that has many industrial applications. Traditionally, the catalytic processes involved in the oxidation of alkenes produce a great deal of environmentally undesirable wastes. Therefore, the development of green processes for the catalytic oxidation of alkenes is becoming increasingly important. To achieve the green catalytic processes is to develop new efficient catalysts.Metal-organic frameworks (MOFs) are crystalline solids, whose structures are constructed from metal ions or clusters coordinated to polytopic organic ligands. MOFs have follow advantages:(1) Large specific surface area and pore volume, (2) highly ordered pore structure and highly dispersed unsaturated metal ion sites, (3) easy design, modification and modulation, etc. These merits lead to the facts that MOFs are considered as promising heterogeneous catalysts or catalyst supports. However, the current research in the catalytic oxidation of olefins over MOF-based catalysts is still in infancy.In this thesis, a series of MOF-74(Cu, Co) materials containing both Cu and Co transition metal ions were synthesized by a hydrothermal method using 2,5-dihydroxy terephthalic acid as ligand. The synthesized MOF-74(Cu), MOF-74(Co), and Cu-Co-MOF-74 were characterized by various techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The aerobic oxidation of either cyclohexene or styrene was carried out over the synthesized MOFs in the absence of solvent under the mild conditions. The obtained main results are summarized as follows:1. Metal-organic frameworks simultaneously containing Cu2+ and Co2+, which have the same framework as MOF-74, can be synthesized by a hydrothermal method; Moreover, both Cu2+ and Co2+ can be uniformly dispersed in MOF-74 and their contents are controllable.2. Cu-Co-MOF-74 can catalyze the oxidation of cyclohexene to 2-cyclohexenol and 2-cyclohexen-l-one in the absence of solvent with O2 as oxidant and under the mild reaction conditions. Additionally, both Cu2+ and Co2+ contents in Cu-Co-MOF-74 significantly affect the conversion of cyclohexene and the selectivity for the products.3. In the absence of a solvent with O2 as the oxidant and under the mild reaction conditions, MOF-74(Cu) does show any catalytic activity in the oxidation of styrene, MOF-74(Co) can mainly catalyze the polymerization of styrene, Cu-Co-MOF-74 can mainly catalyze the epoxidization of ethylene in styrene. In addition, with increasing Co2+ content in the Cu-Co-MOF-74, the conversion of styrene and the product of styrene oxide can be enhanced.Novelty of the thesis research:Cu-Co-MOF-74 catalysts can be synthesized, and by changing the ratios of Cu2+ to Co2+ in the catalysts, the catalytic performance on the oxidation of either cyclohexene or styrene can be optimized. The current research also provides some guidance in the development of MOFs as highly stable, adjustably heterogeneous catalysts for the selective oxidation of olefins.