Chlorine‐Free Depolymerization of Commercial PMMA via Oxygen‐Centered Radicals

Mid‐chain depolymerization enables chemical recycling of conventional plastics with carbon–carbon backbones into high‐purity monomers under mild conditions and without any weak bonds typically installed by controlled radical polymerization. However, current reports of mid‐chain depolymerization either suffer from poor reaction yields or rely on an excess of chlorinated solvents to generate only a small fraction of chlorinated radicals with corrosive byproducts. Herein, we introduce a chlorine‐free photothermal mid‐chain depolymerization methodology, which proceeds through a distinct oxygen‐centered radical pathway. In the presence of ppm concentrations of anthraquinone, an efficient photocatalyst, up to 97% monomer can be successfully regenerated, while varying the catalyst loading allows the depolymerization rate to be modulated on demand. Notably, a wide range of commercial materials, such as Plexiglas, acrylic tubes, and light guide plates, can undergo efficient depolymerization, while temporal control could also be demonstrated via iterative “on/off” cycles.