Rational Selection Of Catalysts For Rapid, Low-Energy Chemical Recycling Of Polymers

The discovery of fundamental rules informs the rational selection of catalysts to minimise energy input and maximise performance in the chemical recycling of polymers into pure monomers.

Polymers continue to shape the modern world, yet their use presents a critical sustainability challenge due to mismanaged plastic waste, reliance on fossil resources, and ever-growing carbon dioxide emissions across their lifecycles.

The chemical recycling of polymers back to monomers is a promising waste mitigation strategy because it overcomes the material losses and property degradation that are problematic in mechanical recycling. However, matching the right catalyst to a target polymer remains very challenging.

A new study from the Department of Chemistry at the University of York (team of Prof. Antoine Buchard; Green Chemistry Centre of Excellence) and the University of Oxford (team of Prof. Charlotte K. Williams) has identified a series of simple, selective metal catalysts for the rapid chemical recycling of polyesters and polycarbonates by depolymerisation to cyclic monomers.

The work reveals a general link between the Lewis acidity of the metals and their catalytic activity, which applies to the entire range of polymers tested. The best catalysts feature metals with intermediate acidity, with zinc(II) being always the most active, thanks to its ability to balance competing entropic and enthalpic transition-state barriers to depolymerisation.

The discovery of this relationship between catalyst structure and depolymerisation performance has been published in Journal of the American Chemical Society. Importantly, this new fundamental insight enables the rational selection of both the polymer and catalyst to deliver the fastest and lowest energy chemical recycling.

The study, sponsored by the Royal Society, the EPSRC UK Catalysis Hub and Sustainable Chemicals and Materials Manufacturing Hub (SCHEMA Hub), will be important to minimise energy input and maximise performance in future recycling processes, and to enhance the circularity of polymeric materials.