Multi-Functional Organofluoride Catalysts for Polyesters Production and Upcycling Degradation

Recycling Polyester and Polycarbonate Plastics with Carbocation Lewis Acidic Organocatalysts

The effective management of plastic waste is critical for environmental sustainability. This work explores the use of carbocation catalysts for the recycling of common polyesters and polycarbonates through alcoholysis. We demonstrate complete depolymerization of end-of-life materials and investigate the relationship between the catalytic reactivity and the structural features of the carbocation compounds, including the cations and their counteranions. Carbocations function as Lewis acids, facilitating the interaction with carbonyls in polymer chains. Moreover, our approach enables the hierarchical degradation of the polyester blends. This research not only elucidates the catalytic role of carbocations in the alcoholysis of these polymers, but also establishes a metal-free process for the efficient recycling of waste plastics.

Advancing H-Bonding Organocatalysis for Ring-Opening Polymerization: Intramolecular Activation of Initiator/Chain End

Organocatalytic ring-opening polymerization (ROP) of lactones is a green method for accessing renewable and biodegradable polyesters. Developing new organocatalysts with high activity and controllability is a major and challenging research topic in this field. Here, we report a series of organocatalysts to achieve a fast and controlled ROP of lactones. These catalysts incorporate (thio)urea and alkoxide in one molecule and act as initiators in the ROP. Such catalysts enable an effective intramolecular activation of initiator/chain end, as revealed by computational studies, resulting in higher activity and fewer (thio)urea loads than existing (thio)urea/alkoxide binary systems. These organocatalysts exhibit ultrahigh activity comparable to metal complexes, i.e., turnover number up to 900 and turnover of frequency up to 4860 min-1, affording polyesters with tailor-made structure, predicted molecular weights, narrow dispersity, less epimerization, and minimal transesterification. The catalyst synthesis is simple and scalable, allowing widely tuned activities of the ROP.

Solvent-Promoted Catalyst-Free Recycling of Waste Polyester and Polycarbonate Materials

Polymeric materials are indispensable in our daily lives. However, the generation of vast amounts of waste polymers poses significant environmental and ecological challenges. Instead of resorting to landfilling or incineration, strategies for polymer recycling offer a promising approach to mitigate environmental pollution. Pioneering studies have demonstrated the alcoholysis of waste polyesters and polycarbonates; however, these processes typically require the use of catalysts. Moreover, the development of strategies for catalyst removal and recycling is crucial, particularly in some industrial applications. In contrast, we present a catalyst-free method for the alcoholysis of common polyester and polycarbonate materials into small organic molecules. Certain polar organic solvents exhibit remarkable efficiency in polymer degradation under catalyst-free conditions. Employing these polar solvents, both polymer resins and commercially available products could be effectively degraded via alcoholysis. Our design contributes a straightforward route for recycling waste polymeric materials.