Project Overview

Overview

The modern chemical industry is supported by "synthetic chemistry" that builds new bonds by combining compounds with 2 to 5 carbon atoms and/or aromatic hydrocarbons such as benzene, toluene, and xylene obtained by petroleum refining. Among them, polymers formed by repeatedly binding these simple molecules have rapidly become widespread as synthetic resins (plastics). However, looking at modern chemistry from the perspective of "degradation chemistry", we realize that we have insufficient reactions or catalysts (tools) to disconnect the intermolecular bonds of macromolecules and decompose them into simple small molecules. Now, we should make progress in basic research that responds to the demands of society from the perspective of "degradation chemistry". In recent years, intensive efforts have been devoted to the recycling of plastic wastes. For example, polyalkylene terephthalate, often used as PET bottles, can be subjected to material recycling and monomer recycling by the state of art technology. Polystyrene used in food packaging and polymethylmethacrylate used as organic glass can be decomposed into monomers by heating. On the other hand, there are many persistent plastics for which environmentally friendly recycling methods have not yet been established. For example, thermosetting resins such as epoxy resins and engineering plastics with high heat resistance such as polycarbonate are extremely difficult to decompose. In addition, polyolefin (a general term for polyethylene and polypropylene) which makes up about half of the total plastic production, often used for containers and packaging, is mainly recycled by gasification and oilification. Since this method requires a large amount of energy, energy saving is required from the viewpoint of life cycle assessment (LCA).

Against such a background, this research aims to provide new solutions to the above-mentioned problems from basic science. We will develop catalysts for degrading plastics at the molecular level or for recycling and upcycling (creating new useful raw materials). While development of a heterogeneous catalyst (solid catalyst) that can be recovered and reused is indispensable for social implementation, difficulty in precise structural control of heterogeneous catalysts often prevents them from effective improvement based on understanding of the reaction mechanisms. Here, we focus our attention on the cooperative effect (neighboring-group effect in catalysis) played by the functional group(s) adjacent to the active metal centers in the catalyst. The effect has been attracting attention in recent years in homogeneous catalysts. We propose to expand this concept to heterogeneous catalysts, aiming at the development of well-defined recoverable and reusable catalysts with higher efficiency for plastic degradation.