By: Mimi Martinez
The ample use of single use plastics -such as plastic packing, utensils, and bottles- has contributed to the plastic recycling crisis as many of these materials are not easy to recycle, being highly energy intensive to recycled as well as producing low quality materials as an output of the recycling methods.
Chemical recycling currently accounts for less than 0.1% of the total plastic production. One of the main challenges is that over 77% of plastics are derived from vinyl polymers, such as polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), and polystyrene (PS). These plastics have molecular backbones made up of strong carbon-carbon (C–C) and carbon-hydrogen (C–H) bonds, which are difficult to break due to their high bond dissociation energies (BDE). However, recent advancements in photocatalysis have shown promise in efficiently modifying these strong bonds in small-molecule transformations. By utilizing photon energy, this method allows for selective upcycling of plastics under mild reaction conditions, offering a more energy-efficient alternative to traditional thermal cracking, which typically requires higher temperatures and more intensive processes.
A new study[i] introduces a method using a common organic catalyst, PTH-3CN, that harnesses visible light to break down various types of plastic waste like polyethylene terephthalate (PET), PE, PP, PS, PVC, polyurethanes (PU), PC, and others. This process operates under mild conditions with minimal catalyst (500 ppm), requires no additional acids or metals, and works well with mixed and post-consumer plastics. Mechanistically, PTH-3CN transforms into active compounds that efficiently degrade plastics through a photo-induced electron transfer mechanism. This approach shows promise for scalable and sustainable plastic upcycling.
