Catalyst metal-ligand design for rapid, selective, and solventless depolymerization of Nylon-6 plastics

Developing effective catalysis to address end -of -life Nylon pollution is urgent yet remains underdeveloped. Nylon -6 is a resilient synthetic plastic and a major contributor to ocean pollution. Here, we report a metallocene catalytic system based on earth -abundant early transition and lanthanide metals that mediates Nylon -6 depolymerization at unprecedented rates up to 810 (epsilon-caprolactam)center dot mol(Cat.)-1 center dot h-1 at 240 degrees C in R99% yield. This solventless process operates with catalyst loadings as low as 0.04 mol % at temperatures as low as 220 degrees C-the mildest Nylon -6 depolymerization conditions reported to date. This metallocene catalysis can be carried out in a simulated continuous process, and the resulting epsilon-caprolactam can be re -polymerized to higher -quality Nylon -6. Experimental and DFT analyses identify effective depolymerization pathways involving catalytic intra-Nylon-chain "unzipping"assisted by p-ligand effects and inter -chain "hopping."A robust chelating ansa-yttrocene is particularly effective in depolymerizing diverse commodity end -of -life articles, such as fishing nets, carpets, clothing, and plastic mixtures.