Photothermal Mediated Chemical Recycling to Monomers via Carbon Quantum Dots

Plastic recycling strategies to combat rapidly increasing waste buildup are of utmost environmental importance. Chemical recycling to monomers has emerged as a powerful strategy that enables infinite recyclability through depolymerization. However, methods for chemical recycling to monomers typically rely on bulk heating of polymers, which leads to unselective depolymerization in complex polymer mixtures and the formation of degradation byproducts. Here, we report a selective chemical recycling strategy facilitated by photothermal carbon quantum dots under visible light irradiation. Upon photoexcitation, we found that carbon quantum dots generate thermal gradients that induce depolymerization of various polymer classes, including commodity and postconsumer waste plastics, in a solvent-free system. This method also provides selective depolymerization in a mixture of polymers, not possible by bulk heating alone, enabled by localized photothermal heat gradients and the subsequent spatial control imparted over radical generation. Photothermal conversion by metal-free nanomaterials facilitates chemical recycling to monomers, an important approach in addressing the plastic waste crisis. More broadly, photothermal catalysis enables challenging C-C bond cleavages with the generality of heating but without indiscriminate side reactions typical of bulk thermolysis processes.