Metal-Organic Framework-Gated Biocatalysis Enables Triggered Depolymerization of Melt-Processed Polyesters

Area of Science:

• Materials Science
• Biocatalysis
• Polymer Chemistry

Background:

• Enzyme deactivation at high temperatures hinders biocatalytic applications in melt-processed polymers.
• Controlled depolymerization of common plastics like PCL, PBAT, and PLA remains a significant environmental challenge.

Purpose of the Study:

• To develop a method for preserving enzyme activity during polymer melt processing.
• To enable triggered, on-demand depolymerization of polyesters using encapsulated enzymes.

Main Methods:

• Encapsulation of enzymes within zeolitic imidazolate framework-8 (ZIF-8) to create Enzyme@ZIF-8 biocomposites.
• Compounding of Enzyme@ZIF-8 with PCL, PBAT, and PLA using twin-screw extrusion.
• Assessment of enzyme activity retention, polymer mechanical properties, and degradation rates after chemical triggering.

Main Results:

• Enzyme@ZIF-8 retained >85% activity after 2 minutes at 180°C.
• Biocomposite production achieved ~50 kg/day, scalable to tonne-per-day compounding.
• Enzyme@ZIF/plastic composites maintained mechanical properties comparable to neat polymers.
• Depolymerization rates increased 13.3-62.8-fold for PCL and PLA, and 1.7-fold for PBAT, with triggered release.

Conclusions:

• Metal-organic framework-gated biocatalysis offers a viable strategy for melt-processable, triggered polymer depolymerization.
• This platform is compatible with industrial polymer manufacturing and enhances end-of-life options for polyesters.
• The approach facilitates efficient and controlled degradation of plastics, addressing key environmental concerns.