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

Liwei Ye, Xiaoyang Liu, Kristen B. Beckett, Jacob O. Rothbaum, Clarissa Lincoln, Linda J. Broadbelt*, Yosi Kratish*, Tobin J. Marks*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

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 (ε-caprolactam)·mol(Cat.)−1·h−1 at 240°C in ≥99% yield. This solventless process operates with catalyst loadings as low as 0.04 mol % at temperatures as low as 220°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 ε-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 π-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.

Original languageEnglish (US)
Pages (from-to)172-189
Number of pages18
JournalChem
Volume10
Issue number1
DOIs
StatePublished - Jan 11 2024

Keywords

  • Nylon
  • SDG11: Sustainable cities and communities
  • SDG9: Industry, innovation, and infrastructure
  • catalysis
  • depolymerization
  • end-of-life plastic
  • fishing net recycling
  • ligand design
  • metallocene catalysts
  • ocean plastics
  • plastic circularity
  • plastic recycling

ASJC Scopus subject areas

  • General Chemistry
  • Biochemistry
  • Environmental Chemistry
  • General Chemical Engineering
  • Biochemistry, medical
  • Materials Chemistry

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