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Compartmentalization of homogeneous catalysts enhances their catalytic performance and can even increase the selectivity. Microgels can serve as smart catalyst carrier systems offering the compartmentalization combined with good accessibility of the catalyst enabling the recyclability and re‐usability. Yet, the incorporation of coordination complexes into microgels has not been studied systematically, lacking in detailed insight in their structure and catalytic performance. Herein, microgels are synthesized with controlled number and localization of copper(II)‐pyrazolyl‐complexes. The catalytic activity of microgels in the Henry reactions is examined showing significantly higher yields compared to pure copper(II)‐pyrazolyl‐complexes. Furthermore, the localization of the copper(II)‐pyrazolyl‐complexes in the microgel core resulted in higher product yields than for microgel catalysts with copper(II) complexes in the shell. Microgel catalysts are demonstrated with copper(II) complexes that can be used in numerous reaction cycles, allow re‐loading of copper to recover catalytically active centers, and can be applicable in industrially‐relevant catalytic processes. [ABSTRACT FROM AUTHOR]

In this study, the aliphatic N,N‐bisguanidine zinc complex [Zn(DMEG2ch)2](OTf)2 ⋅ THF is introduced as a promising candidate for the chemical recycling of (bio) polyesters. This catalyst is highly active in the ring‐opening polymerization (ROP) of lactide (LA) and ϵ‐caprolactone (CL). The combination of polymerization and depolymerization activity creates new pathways towards a sustainable circular economy. The catalytic activity of [Zn(DMEG2ch)2](OTf)2 ⋅ THF for the chemical recycling of polylactide (PLA) via alcoholysis was investigated by detailed kinetic and thermodynamic studies. It is shown that various high value‐added alkyl lactates can be obtained efficiently under mild reaction conditions. Catalyst recycling was successfully tested using ethanol for the degradation of PLA. In addition, LA can be recovered directly from PLA, enabling either open‐ or closed‐loop recycling. Selective PLA degradation from mixtures with polyethylene terephthalate (PET) and polymer blends are presented. For the first time, a cascade recycling reaction of a PLA/polycaprolactone (PCL) blend is tested with a zinc‐based bisguanidine catalyst, whereby PLA is degraded selectively at first and subsequent modification of the reaction conditions leads to efficient degradation of the remaining PCL. The highly active, universally applicable benign zinc catalyst allows the implementation of a circular plastics economy and thus the reduction of plastic pollution in the environment. [ABSTRACT FROM AUTHOR]

In a previous study, we showed that the properties and the ability as an entatic state model of copper guanidine quinoline complexes are significantly influenced by a methyl or methyl ester substituent in the 2-position. To prove the importance of the 2-position of the substituent, two novel guanidine quinoline ligands with a methyl or methyl ester substituent in the 4-position and the corresponding copper complexes were synthesized and characterized in this study. The influence of the substituent position on the copper complexes was investigated with various experimental and theoretical methods. The molecular structures of the copper complexes were examined in the solid state by single-crystal X-ray diffraction (SCXRD) and by density functional theory (DFT) calculations indicating a strong dependency on the substituent position compared to the systems substituted in the 2-position from the previous study. Further, the significantly different influence on the donor properties in dependency on the substituent position was analyzed with natural bond orbital (NBO) calculations. By the determination of the redox potentials, the impact on the electrochemical stabilization was examined. With regard to further previously analyzed guanidine quinoline copper complexes, the electrochemical stabilization was correlated with the charge-transfer energies calculated by NBO analysis and ground state energies, revealing the substituent influence and enabling a comparatively easy and accurate possibility for the theoretical calculation of the relative redox potential. Finally, the electron transfer properties were quantified by determining the electron self-exchange rates via the Marcus theory and by theoretical calculation of the reorganization energies via Nelsen's four-point method. The results gave important insights into the dependency between the ability of the copper complexes as entatic state model and the type and position of the substituent. [ABSTRACT FROM AUTHOR]

Herein, we present electrochemical depolymerisation as a promising new technique for chemical recycling of polylactic acid. Using platinum electrodes and a current density of 50 mA cm−2, a maximum yield of 87% lactic acid was obtained. Moreover, first mechanistic insights, the effect of the reaction conditions, and application to real waste streams are discussed in the following. [ABSTRACT FROM AUTHOR]

In the modern world, plastics have become indispensable. Due to their properties, they are used for a wide variety of applications ranging from packaging materials to textiles and medical technology. The vast majority of these plastics are made from finite fossil feedstocks that will need to be replaced in the long term to meet consumer demands in the future. Intensive research is being conducted into alternative bio‐based feedstocks to replace petroleum‐based plastics with more environmentally friendly variants. This includes polylactide, a polyester derived from lactic acid, which is mainly used as packaging material. In this work, star‐shaped copolymers consisting of polylactide and OrganoCat lignin with varying lignin loadings are synthesized using a "grafting‐from" approach directly from the lactide melt using a zinc‐based guanidine catalyst. This method proves to be efficient and copolymers can be produced after 30 min to three hours with high lactide conversions. Kinetic studies are performed to investigate the influence of different lignin loadings on the polymerization rate and 31P NMR experiments are used to analyze the functionalization of the lignin. Thermal analysis reveals an increase of the glass transition temperature and a higher thermal decomposition temperature with increasing lignin content. [ABSTRACT FROM AUTHOR]