Photothermal Mediated Chemical Recycling to Monomers via Carbon Quantum Dots

Plastic recycling strategies to combat rapidly increasingwastebuildup are of utmost environmental importance. Chemical recyclingto monomers has emerged as a powerful strategy that enables infiniterecyclability through depolymerization. However, methods for chemicalrecycling to monomers typically rely on bulk heating of polymers,which leads to unselective depolymerization in complex polymer mixturesand the formation of degradation byproducts. Here, we report a selectivechemical recycling strategy facilitated by photothermal carbon quantumdots under visible light irradiation. Upon photoexcitation, we foundthat carbon quantum dots generate thermal gradients that induce depolymerizationof various polymer classes, including commodity and postconsumer wasteplastics, in a solvent-free system. This method also provides selectivedepolymerization in a mixture of polymers, not possible by bulk heatingalone, enabled by localized photothermal heat gradients and the subsequentspatial control imparted over radical generation. Photothermal conversionby metal-free nanomaterials facilitates chemical recycling to monomers,an important approach in addressing the plastic waste crisis. Morebroadly, photothermal catalysis enables challenging C-C bondcleavages with the generality of heating but without indiscriminateside reactions typical of bulk thermolysis processes.