Mesoporous Manganese Oxide Materials for Aerobic Oxidation Reactions

The thesis presented here is focused on fabricating thermally stable and tunable mesoporous manganese oxide materials for catalytic aerobic oxidation reactions. From the viewpoint of green chemistry, the design of novel methodologies for oxidation, preferably under aerobic atmospheric condition, without any additives is highly desirable. Being motivated by advances in catalytic materials as fundamental pillars of ‘green chemistry’, my research is devoted to designing of useful materials in oxidative catalysis that may serve the purpose of sustainable energy sources in harmony with the environment and nature. The five chapters provided here will discuss the importance of catalytic oxidation reactions, synthesis, and characterization of the mesoporous manganese oxide materials and their applications in a series of simple to complex oxidation reactions. We demonstrate the activity enhancement of mesoporous manganese oxide materials by introducing alkali metal ions in a simple alcohol oxidation reaction. The major achievement of this work is inventing a cesium ion promoted mesoporous manganese oxide, which was found to be active in a multitude of aerobic oxidation reactions. In terms of catalytic oxidation reactions, oxidation of alcohol to aldehydes, amines to imines, a versatile one –pot tandem oxidation processes and oxidative coupling of alkynes have been discussed. Moreover, mechanistic aspects of catalytic oxidation are studied in details, especially the role of the surface oxygen species, oxygen vacancies and related oxygen transportation of the metal oxides. The catalytic oxidation protocols discussed here have several advantages over the existing systems in addressing the goals of green chemistry. First, the heterogeneous nature of the catalyst provides ease of separation of product. Next, excellent reusability of the catalyst (as high as 8 cycles) and formation of water as the only by-product (in most of the cases) reduces toxic waste production. Finally, absence of additives and use of air as the terminal oxidant exemplify the greener, more efficient and less expensive nature of these processes