Researchers at Tokyo Metropolitan University have discovered that gold nanoparticles deposited on the zirconia surface help convert waste products such as biomass and polyester into organosilane compounds, valuable chemicals used in a wide variety of applications. The new protocol takes advantage of the interaction between gold nanoparticles and the amphoteric (both acidic and basic) nature of the zirconia substrate. The result is a reaction that requires less harsh conditions and a more environmentally friendly waste treatment method.

Recycling is a big part of humanity’s solution to the global plastic waste problem. In many ways, it’s about turning plastic waste into plastic products. However, scientists are also exploring alternative approaches to encourage the use of waste as a resource. This involves recycling, turning waste into entirely new compounds and products that may be more valuable than the materials used to make them.

Simple and complex ethers interact with disilane in the presence of a hybrid catalyst consisting of gold nanoparticles fixed on a zirconium oxide substrate. The presence of acidic and basic centers as well as gold nanoparticles on the support helps convert simple and complex ester groups into silane groups.

A research team from Tokyo Metropolitan University led by Associate Professor Hiroki Miura has worked to convert plastics and biomass into organosilanes, which are organic molecules with a silicon atom attached to form a carbon-silicon bond. Organosilanes are valuable materials for high performance coatings and intermediates in the manufacture of pharmaceuticals and agrochemicals. However, the addition of a silicon atom often involves reagents that are sensitive to air and moisture and require high temperatures, let alone harsh acidic or basic conditions. This potentially makes the conversion process itself an environmental burden.

Now the team used a hybrid catalyst consisting of gold nanoparticles deposited on a zirconium oxide substrate. The catalyst takes ether and ester groups found in plastics like polyester and biomass compounds like cellulose and helps them react with a silicon-containing compound known as disilan. With moderate heating in solution, they successfully formed organosilane groups in which a complex or ether group is present. Through a detailed study of the mechanism, the team discovered that the interaction between the gold nanoparticles and the amphoteric (both basic and acidic) nature of the base is responsible for the efficient, high-efficiency conversion of the raw material under temperate conditions.

Given that disposal of plastic waste often requires incineration or harsh acid/alkaline conditions, the process itself already provides an easy way to break down polyesters under much less demanding conditions. But the key point here is that the reaction products themselves are valuable compounds ready for new applications. The team hopes that this new route to organosilane production will be part of our journey towards a carbon-free future, where plastic ends up in products that are more beneficial to society than to the environment.