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PNNP-iridium: A prototypical catalyst framework tailored for diverse hydrogenative depolymerization of polyesters
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Chemists developed a family of iridium-based catalysts that can chemically break polyesters—including PET plastic from bottles—back into their building-block chemicals under mild, potentially solvent-free conditions, enabling chemical recycling rather than downcycling or landfill disposal. Preventing plastic from fragmenting into microplastics in the first place, by recycling it efficiently at the chemical level, is a complementary strategy to cleanup. While this is early-stage chemistry, it demonstrates a versatile platform for upcycling plastic waste into valuable feedstocks.
Abstract Growing concern over marine- and microplastic pollution has intensified the need for efficient polymer upcycling strategies. Herein, we report a family of iridium complexes bearing a PNNP tetradentate ligand, ((PNNP)Ir), as a versatile prototypical platform for the hydrogenative depolymerization of polyesters. Systematic modification of the bipyridine and phosphine substituents enables the conversion of a broad range of polyesters, including commodity plastics, into diols under mild and even solvent-free conditions. Notably, selective semi-hydrogenation of poly(ethylene terephthalate) (PET) is achieved through fine-tuning of the (PNNP)Ir framework. While fully hydrogenative depolymerization proceeds via direct H₂ addition, semi-hydrogenation operates through a H2-free, transfer-hydrogenation pathway. As a result, (PNNP)Ir complexes can utilize diverse hydrogen sources, and both reaction modes are readily extended to deuteration. These findings establish (PNNP)Ir as an exceptionally versatile and pertinent scaffold for the upcycling of polyesters into value-added chemical feedstocks.
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Researchers developed an efficient catalytic system using an NNN-based iron pincer catalyst to depolymerize polyester and polycarbonate plastics via hydrogenative methods, enabling either methanolysis into ester monomers or transfer hydrogenation into value-added products. The system provides an eco-friendly alternative for chemical upcycling of plastic waste, addressing the significant environmental burden of polyester accumulation.
Noncovalent Interaction-Catalyzed High Conversion of Waste PET Plastics into Organic Esters under Mild Conditions
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Scientists found a gentle, energy-efficient way to break down PET plastic (the type used in water bottles and food containers) into valuable chemical building blocks that can be reused, using a special catalyst that works like a molecular "unlocking" tool. This matters because most plastic recycling is inefficient or requires harsh conditions, so better methods to fully break down plastic waste could reduce the amount of PET that ends up polluting our environment and breaking into microplastics that we may end up breathing or eating.
Recent advances in catalytic hydrogenolysis of polyester
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This review summarises a decade of research into chemically recycling polyester plastic waste (especially PET) by breaking its polymer chains using hydrogen gas — a process called hydrogenolysis — to recover valuable chemical building blocks. Different catalysts allow scientists to target different chemical bonds in PET, yielding products like aromatic hydrocarbons, glycols, or terephthalic acid under varying conditions. Developing efficient chemical recycling pathways is directly relevant to reducing plastic waste and the microplastic pollution that results from improperly disposed plastics.
Chemical recycling of post-consumer polyester wastes using a tertiary amine organocatalyst
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Researchers developed a metal-free chemical recycling method using a common amine catalyst to break down PET and other polyesters from post-consumer plastic waste — including textiles and multilayer packaging — into reusable monomers with 100% yield. This technique offers a simpler, more efficient path to closing the plastic recycling loop.
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Researchers developed a ruthenium-based catalyst that depolymerizes polyesters—including PLA and PET—into reusable diols under mild conditions, with PLA breaking down at room temperature and just 1 MPa hydrogen pressure, enabling selective upcycling of mixed plastic waste including polyolefins.
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When a large batch of papers lands in the Atlas, we read through it and send a short write-up of what stood out.