# All‐Round Talent: Unique Zinc Guanidine Catalyst Performs Efficiently in Synthesis and Chemical Recycling of (Bio)Polyesters

## TL;DR

A new zinc catalyst efficiently produces and recycles bio-based plastics, supporting a circular economy.

## Contribution

A novel zinc guanidine complex shows exceptional performance in both polymerization and depolymerization of (bio)polyesters.

## Key findings

- The catalyst [Zn{(R,R)TMGNMe2(1,2)ch}2](OTf)2 achieves high activity in polymerizing lactide and caprolactone.
- It enables polylactide with a molar mass of up to 118,000 g mol−1 under bulk conditions.
- The catalyst can be reused up to nine times for polyester recycling without losing activity.

## Abstract

In this study, two new hybrid guanidine ligands are presented that serve as the basis for the preparation of six new zinc‐hybrid guanidine complexes. The complex [Zn{(R,R)TMGNMe2(1,2)ch}2](OTf)2 (C1) shows a very high catalytic activity toward lactide and caprolactone ring‐opening polymerization (ROP) under industrially relevant bulk conditions. Using recrystallized l‐lactide, polylactide with a molar mass of up to 118 000 g mol−1 can be produced. The extremely fast caprolactone polymerization highlights the versatility of C1, as the polymerization rate constants are of the same order of magnitude. This is further underlined by high activity toward the chemical recycling of polyesters. In particular, C1 can be recycled highly efficiently, performing methanolysis and ethanolysis of polylactide up to nine times without any loss of activity. By combining efficient polymerization and depolymerization of (bio)polyesters, new catalyst paves the way toward a circular plastics economy.

A new zinc hybrid guanidine catalyst [Zn{(R,R)TMGNMe2(1,2)ch}2](OTf)2 (C1) shows very high catalytic activity in the polymerization of cyclic esters and in the depolymerization of these polyesters. Using C1 in the ring‐opening polymerization of lactide and caprolactone under industrially relevant conditions, astonishing rate constants of the same order of magnitude are obtained. The recyclability of the catalyst in methanolysis is particularly outstanding.