Light‐Driven Waste‐To‐Value Upcycling: Bio‐Based Polyols and Polyurethanes from the Photo‐Oxygenation of Cardanols

The upcycling of waste biomass into valuable materials by resource‐efficient chemical transformations is a prime objective for sustainable chemistry. This approach is demonstrated in a straightforward light‐driven synthesis of polyols and polyurethane foams from the multi‐ton waste products of cashew nut processing. The photo‐oxygenation of cardanol from nutshell oil results in the formation of synthetically versatile hydroperoxides. The choice of the workup method (i. e., reduction, hydrogenation, epoxidation) enables access to a diverse range of alcohols with tunable alkene and OH functions. Condensation with isocyanates to give rigid polyurethane foams provides a resource‐efficient waste‐to‐value chain that benefits from the availability of cardanol and installation of OH groups from aerial O(2).