Light-Controlled Chemical Recycling of Plastics: A Programmable One-Pot Solution

Monomer yields surpassing 80% were achieved from nine distinct real-world post-consumer plastics. This is the headline figure from a new study addressing the most stubborn barrier in waste management: mixed streams. Current infrastructure fails to separate complex polyester mixtures effectively. This failure mandates the chemical recycling of plastics through more intelligent, molecular means.

Chemical recycling of plastics via programmable light

The core innovation is a ‘one-pot’ photothermal strategy. Researchers synthesised a catalyst from a bimetallic Metal-Organic Framework (Zn/Co-ZIF-C). It absorbs broadband light and converts it to heat with extreme precision. The breakthrough lies in selectability. Operators do not need to separate the waste physically. Instead, they programme the light source.

Specific irradiation intensities trigger the breakdown of specific polymers:

• 420 mW cm^-2: Triggers glycolysis of Polycarbonate (PC).
• 520 mW cm^-2: Depolymerises Polylactic acid (PLA).
• 650 mW cm^-2: Breaks down Polyethylene terephthalate (PET).

This sequential activation allows for stepwise monomer recovery from a single mixed batch. The messy reality of unsorted rubbish is managed through precise energy inputs rather than mechanical sorting. Efficiency is paramount.

Mechanistic insights and industrial viability

Density functional theory calculations measured the atomic interactions. Results point to a dual-site cooperative mechanism where ZnO and Co-Nx sites activate ester bonds and ethylene glycol together. This explains the substrate-specific reactivity. The catalyst is not fragile. It maintained over 95% PET conversion efficiency across five cycles. Furthermore, it performed magnetic separation and dye removal simultaneously.

Why this matters is clear. Mixed waste usually ends in landfill or incineration due to the cost of separation. This method suggests a scalable path toward true circularity. It transforms a complex logistical problem into a controllable chemical process, recovering high-value monomers from previously unmanageable trash.