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Researchers at TU Berlin succeed in breaking down silicone to its basic building block - Paper now published in the journal Nature Oct 29, 2026, 5:44:28 PM Stefanie Terp , Technische Universitat Berlin Silicones are widely used in industry, medicine, and everyday products due to their exceptional thermal and chemical stability. However, it is precisely these properties that have made recycling silicones extremely problematic in the past. Researchers at the Institute of Chemistry at TU Berlin have now succeeded in breaking down the polymer chains of silicone molecules into their basic building blocks. The resulting molecule dimethyldichlorosilane can then be reused as a starting material for the production of new silicone compounds. The process is based on a complex interplay of several chemical reaction cycles and the researchers have now applied for a patent. The team led by Professor Dr. Martin Oestreich has successfully tested the process on various silicone products used in everyday life. Given its great significance for green chemistry and the circular economy, the paper was selected by the renowned journal Nature for fast-track online publication. Martin Oestreich is also a member of the UniSysCat Cluster of Excellence specializing in catalysis at TU Berlin.The market for silicone products is huge: In 2025, it totaled more than 21 billion euros, and analysts estimate it will exceed 33 billion euros in 2033. In addition to their thermal and chemical stability, silicones are also characterized by outstanding mechanical properties. Silicone also reliably repels water while allowing oxygen to pass through. Silicones are found in many everyday products - from baking pans and baby bottle nipples to gaskets and medical tubing. Its robust properties make recycling used silicone very difficult, says Professor Dr. Martin Oestreich, Einstein Professor, head of the Organic Chemistry/Synthesis and Catalysis Group at TU Berlin, and a member of the Universitys UniSysCat Cluster of Excellence. Until now, waste silicone has mostly been incinerated or sent to landfill. During recycling, the material is often mechanically processed or chemically broken down into smaller, ring-shaped siloxanes, which can then be used to produce new silicones. However, these are generally of lower quality than the original ones.The production of silicones is extremely energy-intensive, which is why recycling makes a lot of senseOn the one hand, the growing evidence that silicones disposed of in landfills can be harmful to the environment and human health makes their complete recycling an objective worth pursuing. On the other hand, producing silicones requires enormous amounts of energy. For example, the elemental silicon needed has to be extracted from quartz sand at temperatures of 2,000 degrees Celsius. Using this silicon, dimethyldichlorosilane - the basic building block of silicone chemistry - is then produced in a special process. This molecule can be strung together to form long chains, with the chlorine it contains being replaced by oxygen, explains Oestreich. As in carbon chemistry, it is not carbon atoms but the bonds between silicon (Si) and oxygen (O) that form the backbone of the resulting polymers (Si-O-Si-O-Si). The chain length can be varied and various other molecules can be attached to the sides of the chains to determine the properties of different silicones.The key to breaking the silicone chains: Silylium ion as a catalyst and phosgeneAn ideal recycling process would include the ability to produce new silicones with different properties from end-of-life silicones. To achieve this, the base molecule dimethyldichlorosilane must be the end product of the recycling process, says Martin Oestreich. This requires the Si-O-Si chains in the silicones to be completely broken. Breaking the silicon-oxygen bonds is extremely difficult. This is what makes silicone such a stable material. The researchers have now succeeded in doing this, primarily through the use of two molecules: a silylium ion as a catalyst and the gas phosgene. Silylium ions are chemical compounds that contain a positively charged silicon atom. The silylium ion removes a chloride ion (Cl-) from phosgene (COCl2) through a complex interplay of several reaction cycles. What is left is the compound COCl+. This molecule then has the chemical ability to break a silicon-oxygen bond, says Oestreich. Another advantage of the process is that the oxygen from the broken Si-O-Si chains immediately escapes as carbon dioxide (CO2). The oxygen is thus bound in a stable compound and immediately released as a gas. This means it is no longer available for other reactions.Phosgene is toxic, but is used in large quantities in industryPhosgene is a toxic gas. This explains why the researchers did not use it directly, but instead chose the more manageable solid triphosgene, which releases phosgene only during the reaction cycle. This conversion is also catalyzed by the silylium ion, which thus performs a dual function. However, the use of phosgene is by no means uncommon in the chemical industry. For example, key starting materials for polyurethanes - which are used to make foams and insulation materials - are produced using phosgene, explains Martin Oestreich. Despite this, his research group is already working on finding alternatives to phosgene. They are also planning to develop processes to purify dimethyldichlorosilane recovered during the recycling process of even the smallest traces of phosgene.Recycling yield is very high in tests with everyday productsAt temperatures of 80 degrees, the reaction conditions are moderate, and the process can be carried out without significant energy input. The researchers have already tested it on silicone cupcake pans, baby bottle nipples, silicone lids, and other silicone products. The results proved promising: For some products, the yield of recovered dimethyldichlorosilane after 24 hours was as high as 99 percent. A mixtur
