A Multitool for Circular Economy: Fast Ring-Opening Polymerization and Chemical Recycling of (Bio)polyesters Using a Single Aliphatic Guanidine Carboxy Zinc Catalyst.

Invited for this month's cover is the group of Professor Sonja Herres-Pawlis at the RWTH Aachen (Germany). The cover image illustrates the complex yet flexible circular economy of (bio)plastics and the role of a Zn-based catalyst therein. The Research Article itself is available at 10.1002/cssc.202300192.

A Multitool for Circular Economy: Fast Ring-Opening Polymerization and Chemical Recycling of (Bio)polyesters Using a Single Aliphatic Guanidine Carboxy Zinc Catalyst.

A new aliphatic hybrid guanidine N,O-donor ligand (TMGeech) and its zinc chloride complex ([ZnCl2 (TMGeech)]) are presented. This complex displays high catalytic activity for the ring-opening polymerization (ROP) of lactide in toluene, exceeding the toxic industry standard tin octanoate by a factor of 10. The high catalytic activity of [ZnCl2 (TMGeech)] is further demonstrated under industrially preferred melt conditions, reaching high lactide conversions within seconds. To bridge the gap towards a sustainable circular (bio)economy, the catalytic activity of [ZnCl2 (TMGeech)] for the chemical recycling of polylactide (PLA) by alcoholysis in THF is investigated. Fast production of different value-added lactates at mild temperatures is demonstrated. Selective PLA degradation from mixtures with polyethylene terephthalate (PET) and a polymer blend, catalyst recycling, and a detailed kinetic analysis are presented. For the first time, chemical recycling of post-consumer PET producing different value-added materials is demonstrated using a guanidine-based zinc catalyst. Therefore, [ZnCl2 (TMGeech)] is a promising, highly active multitool, not only to implement a circular (bio)plastics economy, but also to tackle today's ongoing plastics pollution.

Switchable Catalytic Polyoxometalate-Based Systems for Biomass Conversion to Carboxylic Acids.

We present the Keggin-type polyoxometalate H6[PV3Mo9O40] as a switchable catalyst being able to catalyze the transformation of both glucose and glyceraldehyde to formic acid (42%) and lactic acid (40%), respectively, within 1 h reaction time by simply changing the reaction atmosphere at 160 °C from oxygen to nitrogen in one reactor setup. In detail, we report the influence of different gas atmospheres and reaction temperatures on various vanadium-containing catalysts in the selective transformation of several biogenic substrates to carboxylic acids with a special emphasis on reaction pathways and switchability of the catalyst systems. All investigations were carried out in parallel using either an oxygen or a nitrogen atmosphere of 20 bar performing time-resolved experiments between 0.25 and 5 h and a temperature variation from 160 to 200 °C. Furthermore, a catalyst and a substrate variation led to the reaction system consisting of glyceraldehyde and the Keggin-type polyoxometalates (POM) H6[PV3Mo9O40] as the best switchable reaction system under the applied conditions. This study shows interesting potential for using both Keggin-type and Lindqvist-type POMs as switchable catalysts for selective biomass conversion to platform chemicals.