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Pharmaceutical and veterinary products are a class of contaminants of emerging concern, and their presence in the environment is due to continuous and incorrect disposal. Environmental scientists have been accumulating data on their adverse effects on animal populations since toxicological effects on wildlife were first published. Therefore, recycling strategies are needed. Valuable active ingredients can be extracted from expired pharmaceuticals and recycled according to various strategies. In an effort to reveal the potential of the chemical upcycling of expired pharmaceuticals, the active ingredients gabapentin and pregabalin were extracted and used as starting materials to prepare a small collection of promising substrates endowed with functionalities and structural three-dimensionality. Gabapentin 1 was transformed into aminoalcohol 3, spiroamine 4, and the bioactive azaspirolactam 5. The lactam analog 6 was synthesized from pregabalin 2. Due to the biological profile of 5 and the structural similarity of the N-alkylated derivatives 5l and 6b with the drug piracetam, a collection of potentially bioactive structural analogs 5a-l and 6a-b were also prepared. Simple extraction, synthesis, and purification procedures were used as a means of chemical and economic revaluation, resulting in moderate to good yields at a low cost. [ABSTRACT FROM AUTHOR]

We present an innovative process for directly transforming poly(ethylene terephthalate) (PET), a polymer extensively used in food and beverage packaging, into trans‐isomer‐enriched 1,4‐cyclohexanedimethanol (CHDM), a key ingredient in advanced specialty polymers. Our approach leverages a dual‐catalyst system featuring palladium on reduced graphene oxide (Pd/r‐GO) and oxalate‐gel‐derived copper‐zinc oxide (og‐CuZn), utilizing hydrogenation/hydrogenolysis relay catalysis. This method efficiently transforms PET into polyethylene‐1,4‐cyclohexanedicarboxylate (PECHD), which is then converted into CHDM with an impressive overall yield of 95 % in a two‐stage process. Our process effectively handles various post‐consumer PET plastics, converting them into CHDM with yields between 78 % and 89 % across different substrates. Additionally, we demonstrate the applicability and scalability of this approach through a temperature‐programmed three‐stage relay process on a 10‐gram scale, which results in purified CHDM with an isolated yield of 87 % and a notably higher trans/cis ratio of up to 4.09/1, far exceeding that of commercially available CHDM. This research not only provides a viable route for repurposing PET waste but also enhances the control of selectivity patterns in multistage relay catalysis. [ABSTRACT FROM AUTHOR]

Polyester plastics, constituting over 10% of the total plastic production, are widely used in packaging, fiber, single‐use beverage bottles, etc. However, their current depolymerization processes face challenges such as non‐broad spectrum recyclability, lack of diversified high‐value‐added depolymerization products, and crucially high energy consumption. Herein, an efficient strategy is developed for dismantling the compact structure of polyester plastics to achieve diverse monomer recovery. Polyester plastics undergo swelling and decrystallization with a low depolymerization energy barrier via synergistic effects of polyfluorine/hydrogen bonding, which is further demonstrated via density functional theory calculations. The swelling process is elucidated through scanning electron microscopy analysis. Obvious destruction of the crystalline region is demonstrated through X‐ray crystal diffractometry curves. PET undergoes different aminolysis efficiently, yielding nine corresponding high‐value‐added monomers via low‐energy upcycling. Furthermore, four types of polyester plastics and five types of blended polyester plastics are closed‐loop recycled, affording diverse monomers with exceeding 90% yields. Kilogram‐scale depolymerization of real polyethylene terephthalate (PET) waste plastics is successfully achieved with a 96% yield. [ABSTRACT FROM AUTHOR]

The environmental impact is a strong incentive for the development of upcycling processes for textile waste. However, toxic chemicals may occur in both brand-new textiles and post-consumer garments, and the chemical transfer in such routes is important to investigate. The present study applied non-target screening and quantification with liquid chromatography/mass spectrometry to follow the fate of hazardous chemicals from post-consumer polycotton garments to a new material, cellulose nanocrystals, in a chemical upcycling utilizing strongly acidic conditions. The majority of hazardous chemicals detected within the process were found to be transferred to a residual of polyester material and not to the enriched cellulose. However, phthalates were found to be mainly attached to the cellulose nanocrystals. The detected total concentration, in this case, was below 5 μg/g, at least 200 times lower than the limit set by the European Union. This indicates the importance of monitoring and controlling the phthalate content in the starting material of the process, i.e., the post-consumer garments. The chemical release into the process waste effluent could be estimated based on water solubility data for chemicals under the applied conditions. Three compounds, the water-repellent substance perfluorooctanesulfonic acid and the dyes Crystal Violet and Victoria Pure Blue, were almost entirely transferred into the process waste effluent. Although the levels detected were very low in the present pilot process, their presence eventually indicates the need for wastewater purification at further upscaling, depending on the exposure and dose in relation to toxicological relevant thresholds.

Recycling of carbon fiber‐reinforced polymer composites (CFRCs) based on thermosetting plastics is difficult. In the present study, high‐performance CFRCs are fabricated through complexation of aromatic pinacol‐cross‐linked polyurethane (PU−AP) thermosets with carbon fiber (CF) cloths. PU−AP thermosets exhibit a breaking strength of 95.5 MPa and toughness of 473.6 MJ m−3 and contain abundant hydrogen‐bonding groups, which can have strong adhesion with CFs. Because of the high interfacial adhesion between CF cloths and PU−AP thermosets and high toughness of PU−AP thermosets, CF/PU−AP composites possess a high tensile strength of >870 MPa. Upon heating in N,N‐dimethylacetamide (DMAc) at 100 °C, the aromatic pinacols in the CF/PU−AP composites can be cleaved, generating non‐destructive CF cloths and linear polymers that can be converted to high‐performance elastomers. The elastomers are mechanically robust, healable, reprocessable, and damage‐resistant with an extremely high tensile strength of 74.2 MPa and fracture energy of 149.6 kJ m−2. As a result, dissociation of CF/PU−AP composites enables the recovery of reusable CF cloths and high‐performance elastomers, thus realizing the upcycling of CF/PU−AP composites. [ABSTRACT FROM AUTHOR]

The total production of global plastics is up to 400 million tons per year. Nearly 80% of the used plastics are directly landfilled or dumped in the environment, leading to the generation and release of microplastics, which poses a great threat to both environment and human health. How to recycle plastic waste efficiently and environmentally has become a common concern worldwide. Among the plastic waste recycling methods, chemical recycling such as pyrolysis can realize the transformation from polymer to high-value products. This paper summarizes the research and industrialization progress of four different plastic waste pyrolysis technologies, namely fast pyrolysis, catalytic pyrolysis, oxidative pyrolysis and hydro-pyrolysis. The challenges faced by the pyrolysis of plastic waste is discussed and the future development direction of various pyrolysis technologies is also outlooked. It is expected that some more efficient, environmentally friendly, and economical technologies of plastic waste pyrolysis can be explored in the future, to meet the growing demand for environmental protection and sustainable development.

Polyolefins consist of abundant hydrophobic C−C and C−H bonds, and are considered as immensely potential untapped resources. Chemical upcycling offers a convenient and promising recycling strategy of polyolefins to produce newly‐functionalized polymeric materials, and high‐value added chemicals. The significant progress made in C−H functionalization reactions of alkane molecules provides new opportunities for improving polyolefin treatments. This review focuses on recent advancements in post‐modification routes, specifically the introduction of C−C and C−X (X=O, N, S, halogens and etc.) bonds onto polyolefin chain backbones, as well as degradation models involving homogeneous C−H functionalization. By emphasizing these developments, we aim to highlight the potential of chemical upcycling for enhancing the treatment of polyolefins. [ABSTRACT FROM AUTHOR]

Chemical upcycling of waste plastics into high‐value‐added products is one of the most effective, cost‐efficient, and environmentally beneficial solutions. Many studies have been published over the past few years on the topic of recycling plastics into usable materials through a process called catalytic pyrolysis. There is a significant research gap that must be bridged in order to use catalytic pyrolysis of waste plastics to produce high‐value products. This review focuses on the enhanced catalytic pyrolysis of waste plastics to produce jet fuel, diesel oil, lubricants, aromatic compounds, syngas, and other gases. Moreover, the reaction mechanism, a brief and critical comparison of different catalytic pyrolysis studies, as well as the techno‐feasibility analysis of waste plastic pyrolysis and the proposed catalytic plastic pyrolysis setup for commercialization is also covered. [ABSTRACT FROM AUTHOR]

Abstract The mass production of disposable polyolefin products has led to serious plastic pollution and an imbalance between manufacturing and recycling. Given these challenges, the chemical upcycling of waste polyolefins has attracted extensive attention due to its high efficiency and economic benefits. Herein, we review the development of polyolefin chemical upcycling in heterogeneous catalysis. The status quo of polyolefin recycling is first discussed. We then introduce the advanced strategies for chemical upcycling in the view of different value‐added products and discuss their challenges and prospects. Our in‐depth analysis centers on the catalytic mechanism and the design principle of heterogeneous catalysts. Finally, we outlook the promising directions to facilitate the degradation process via polymer and catalyst design and optimized catalytic engineering. Innovative strategies are expected to promote the chemical upcycling of polyolefins, bringing great promise for the sustainable development of society.

Converting poly(ethylene terephthalate) (PET) into metal–organic frameworks (MOFs) has emerged as a promising innovation for upcycling of waste plastics. However, previous solvothermal methods suffer from toxic solvent consumption, long reaction time, high pressure, and high temperature. Herein, a mechanochemical milling strategy was reported to transform waste PET into a series of MOFs with high yields. This strategy had the merits of solvent‐free conditions, ambient reaction temperature, short running time, and easy scale‐up for large‐scale production of MOFs. The as‐prepared MOFs exhibited definite crystal structure and porous morphology composed of agglomerated nanoparticles. It was proven that, under mechanochemical milling, PET was firstly decomposed into 1,4‐benzenedicarboxylate, which acted as linkers to coordinate with metal ions for forming fragments, followed by the gradual arrangement of fragments into MOFs. This work not only promotes high value‐added conversion of waste polyesters but also offers a new opportunity to produce MOFs in a green and scalable manner. [ABSTRACT FROM AUTHOR]

The chemical upcycling of polymers is an emerging strategy to transform post‐consumer waste into higher‐value chemicals and materials. However, on account of the high stability of the chemical bonds that constitute their main chains, the chemical modification of many polymers proves to be difficult. Here, we report a versatile approach for the upcycling of linear and cross‐linked polyureas, which are widely used because of their high chemical stability. The treatment of these polymers or their composites with acetylacetone affords di‐vinylogous amide‐terminated compounds in good yield. These products can be reacted with aromatic isocyanates, and the resulting aminoketoenamide bonds are highly dynamic at elevated temperatures. We show here that this conversion scheme can be exploited for the preparation of dynamic covalent poly(aminoketoenamide) networks, which are healable and reprocessable through thermal treatment without any catalyst. [ABSTRACT FROM AUTHOR]

Dynamic covalent polymer networks (DCPN) provide an important solution to the challenging recyclability of thermoset elastomers. However, dynamic bonds exhibit relatively weak bond energies, considerably decreasing the mechanical properties of DCPN. Herein, a novel reinforcement strategy for DCPN involving the in situ formation of supramolecular organic nanofillers through asynchronous polymerization is proposed. Owing to the difference in the reactivity of the isocyanate groups and the gradual deblocking of aldimine, asynchronous cross-linking of hexamethylene diisocyanate and isocyanate-terminated prepolymer containing dynamic oxime-urethane bonds with the deblocked tris(2-aminoethyl)amine facilitates the transition from the molecular interpenetration of chains into immiscible polymerization. This results in thermodynamic incompatibility between the hyperbranched clusters and long chains, inducing a spontaneous formation of supramolecular organic nanofillers. Compared to traditional reinforcement strategies, supramolecular organic nanofillers considerably improve the mechanical properties of DCPN. Furthermore, the supramolecular interactions between hyperbranched clusters and dynamic oxime-urethane bonds enable the network with excellent recyclability. The unique reinforcement and recyclability of the prepared DCPN allow their combination with carbon fibers (CF) to form CF composites with outstanding properties for personal-protection applications, achieving CF composite upcycling. This study offers a novel strategy on the reinforcement of DCPN and the upcycling of high-performance CF composites., (© 2025 Wiley‐VCH GmbH.)

As a petroleum‐derived polyester material, poly(ϵ‐caprolactone) (PCL) plays an essential role in biomedical field due to its excellent biocompatibility and non‐toxicity. With the increasing use of PCL in recent years, its waste disposal has become a significant challenge. To address this challenge, we demonstrate a high‐efficiency organocatalysis strategy for the chemical upcycling of PCL to valuable chemical. Among organocatalysts explored in this article, 1,5,7‐triazabicyclo[4,4,0]dec‐5‐ene (TBD) shows superior performance for transforming end‐of‐life poly(ϵ‐caprolactone) into highly value‐added methyl 6‐hydroxyhexanoate with quantitative conversion in a short time. The endwise unzipping depolymerization mechanism is corroborated by monitoring molecular weight during depolymerization process and 1H NMR control experiments. Furthermore, this approach is also practicable for large‐scale depolymerization for commercial PCL plastics, providing idea for promoting the sustainable development of PCL plastics. [ABSTRACT FROM AUTHOR]

Emerging chemical technologies can upcycle plastic waste by producing high-value polymers and other products. In this work, we study the economic and environmental benefits of deploying an upcycling infrastructure in the continental United States for producing low-density polyethylene (LDPE) and polypropylene (PP) from post-consumer plastic waste. Our analysis is based on a computational framework that integrates techno-economic analysis, life-cycle assessment, and value chain optimization. Our results demonstrate that the infrastructure could generate a market of nearly 20 billion USD per year and that this market is robust to various externalities. Our analysis also indicates that the infrastructure can achieve a plastic-to-plastic degree of circularity of 34% relative to residential plastic waste production, and leads to significant environmental benefits over alternative waste disposal methods, including 69%–75% lower greenhouse gas emissions than waste-to-energy systems and 38 million tonnes of avoided landfill waste per year. • We present a framework for modeling plastic waste upcycling infrastructure in the US. • We show that the upcycling networkinfrastructure could generate a market of nearly $20 billion USD per year. • The network achieves 34% plastic-to-plastic circularity. • The network achieves sustainability benefits relative to landfilling and waste-to-energy systems. [ABSTRACT FROM AUTHOR]

Steel slag is a byproduct generated by the steel manufacturing industry. It poses environmental contamination and health hazards without effective treatment. Upcycling steel slag as a construction material has attracted attention because of its desirable physicochemical properties (strength, durability, and resistance to corrosion). This study provides an overview of the currently available steel-slag upcycling methods for producing construction materials (cement, concrete, and asphalt mixtures). Specifically, this review comprehensively summarises the applications of steel slag in cement, concrete, and asphalt mixtures. It provides valuable insights into the long-term performance of steel-slag-based construction materials. When used in cement and concrete, the active components (CaO and Fe 2 O 3) in steel slag promote the hydration reaction of cement. This results in the formation of hardened products and an improvement in the mechanical properties of concrete. To optimise the performance of the cement and concrete upcycled from steel slag, it is crucial to control the proportion and fineness of steel slag particles and ensure effective curing conditions and mix design. In asphalt mixtures, the high alkalinity of steel slag improves its adhesion to the asphalt materials. However, owing to the presence of free calcium oxide (f-CaO) in steel slag, the pavement with asphalt upcycled from steel slag causes an expansion associated with the service life of the pavement. The current limitations of steel slag upcycling in construction materials are discussed, and future research directions are recommended. It is anticipated that this review would support the sustainable implementation of steel slag as a raw material for construction. • Steel slag (SS) is steel-manufacturing-industry byproduct requiring proper upcycling. • SS has strength, durability & corrosion resistance, applied to construction material. • SS's proportion/fineness & curing condition/mix design are crucial to use as concrete & cement. • Free calcium oxide in SS is concern for its upcycling as asphalt. [ABSTRACT FROM AUTHOR]

ZnII‐complexes bearing half‐salan ligands were exploited in the mild and selective chemical upcycling of various commercial polyesters and polycarbonates. Remarkably, we report the first example of discrete metal‐mediated poly(bisphenol A carbonate) (BPA‐PC) methanolysis being appreciably active at room temperature. Indeed, Zn(2)2 and Zn(2)Et achieved complete BPA‐PC consumption within 12–18 mins in 2‐Me‐THF, noting high bisphenol A (BPA) yields (SBPA=85–91 %) within 2–4 h. Further kinetic analysis found such catalysts to possess kapp values of 0.28±0.040 and 0.47±0.049 min−1 respectively at 4 wt%, the highest reported to date. A completely circular upcycling approach to plastic waste was demonstrated through the production of several renewable poly(ester‐amide)s (PEAs), based on a terephthalamide monomer derived from bottle‐grade poly(ethylene terephthalate) (PET), which exhibited excellent thermal properties. [ABSTRACT FROM AUTHOR]

As the production volume of polymers increases, so does the amount of plastic waste. Plastic recycling is one of the concepts to address in this issue. Unfortunately, only a small fraction of plastic waste is recycled. Even with the development of polymers for closed loop recycling that can be in theory reprocessed infinitely the inherent dilemma is that because of collection, cleaning and separation processes the obtained materials simply are not cost competitive with virgin materials. Chemical upcycling, the conversion of polymers to higher valuable products, either polymeric or monomeric, could mitigate this issue. In the following article, we highlight recent examples in this young but fast-growing field. This article is part of the theme issue 'Bio-derived and bioinspired sustainable advanced materials for emerging technologies (part 2)'. [ABSTRACT FROM AUTHOR]

Plastic waste, which is one of the major sources of pollution in the landfills and oceans, has raised global concern, primarily due to the huge production rate, high durability, and the lack of utilization of the available waste management techniques. Recycling methods are preferable to reduce the impact of plastic pollution to some extent. However, most of the recycling techniques are associated with different drawbacks, high cost and downgrading of product quality being among the notable ones. The sustainable option here is to upcycle the plastic waste to create high‐value materials to compensate for the cost of production. Several upcycling techniques are constantly being investigated and explored, which is currently the only economical option to resolve the plastic waste issue. This Review provides a comprehensive insight on the promising chemical routes available for upcycling of the most widely used plastic and mixed plastic wastes. The challenges inherent to these processes, the recent advances, and the significant role of the science and research community in resolving these issues are further emphasized. [ABSTRACT FROM AUTHOR]

The massive generation of plastic wastes without satisfactory treatment has induced severe environmental problems and gained increasing attentions. In this Minireview, recent progresses in the chemical upcycling of plastic wastes by using various methods (mainly in the past three to five years) is summarized. The chemical upcycling of plastic wastes points out a "plastic‐based refinery" concept, which is to use the plastic wastes as platform feedstocks to produce highly valuable monomeric or oligomeric compounds, putting the plastic wastes back into a circular economy. The different chemical methods to upcycle plastic wastes, including hydrogenolysis, photocatalysis, pyrolysis, solvolysis, and others, are introduced in each section to valorize diverse plastic feedstocks into value‐added chemicals, materials, or fuels. In addition, other emerging technologies as well as the new generation of plastic thermosets are covered. [ABSTRACT FROM AUTHOR]

The linear approach to resource utilization has led to the accumulation of waste plastic in the environment for decades. Unfortunately, both traditional mechanical recycling and incineration have faced their bottlenecks that have always resulted in quality deterioration and value recovery failures. Recently, chemical recycling and upcycling processes, including the conversion of plastics into their virgin monomers, liquid fuels, or chemical feedstocks to produce value‐added products, have been identified as the most promising strategy for recovering value from waste plastics. However, these methods are often cost prohibitive and relying on stringent conditions compared to current recycling methods. Accordingly, this Minireview summarizes recent trends and achievements in the chemical recycling and upcycling of waste plastics. We highlight three research topics: depolymerization of plastics into monomers; degradation of plastics into liquid fuels and waxes; and conversion of plastics into hydrogen, fine chemical feedstocks, and value‐added functional materials. Indeed, chemical recycling and upcycling is a bright path to a circular and environmentally friendly plastic economy. [ABSTRACT FROM AUTHOR]

Chemical upcycling of plastic waste from landfills to value-added products offers both economic and environmental benefits. Reported here is a simple method to convert high-density polyethylene (HDPE) into upcycled waxes in a very high yield (up to 93%). This selectivity is achieved by reducing the degradation temperature of HDPE via the addition of an inexpensive and reusable sodium chloride. These upcycled waxes had performance comparable to those of commercial rheology modifiers. In addition, kraft paper coated with these upcycled waxes exhibited excellent water- and oil resistance. A preliminary revenue analysis showed that this innovation allows plastic-to-wax to conversion with a three-fold revenue benefit over traditional ways of producing pyrolysis waxes from plastics. Also, sodium chloride reduces the pyrolysis temperature, thus reducing energy consumption and greenhouse gas emissions, supporting cleaner production, a circular economy, and generating less environmental pollution. The underlying concept reported herein can be extended to major plastics by reducing the degradation temperatures of plastics, thereby obtaining even better control over the pyrolysis products. Thus, these findings have the potential to enhance the circular economy of plastics and protect our environment from plastic waste. SYNOPSIS. Chemical upcycling of post-consumer polyethylene via a sodium chloride-catalyzed process. [Display omitted] • Demonstrated table salt-assisted pyrolysis of high-density polyethylene. • Converted polyethylene into upcycled waxes at mild temperatures and in high-yield. • Used upcycled waxes as rheology modifiers and water-proof coating material. • Performed preliminary revenue analysis. [ABSTRACT FROM AUTHOR]

This paper focuses explicitly on the chemical approaches involved in the recycling of polyethylene terephthalate (PET). Due to the high rate of consumption as well as nonbiodegradability, PET plays a crucial role as one of the most significant sources of accumulated waste in the landfill which jeopardizes our planet. To address this issue as well as increased environmentally conscious, running out of landfill space, natural resource, and energy conservation, and producing value‐added chemicals to use as building block or co‐products, the chemical recycling methods have been evolved. Therefore, there has been an attempt to have a comprehensive review of the five types of conventional recycling methods namely hydrolysis, methanolysis, glycolysis, aminolysis, and ammonolysis studied by researchers over the last two decades. In this regard, the influence of diverse depolymerization reaction variables for instance, traditional catalyst, temperature profile, ionic liquid catalysts, phase transfer catalyst, microwave assistance, etc was reported. Moreover, the upsides and downsides of each technique were considered. [ABSTRACT FROM AUTHOR]

Accumulation of mismanaged plastic in the environment and the appearance of emerging plastic-derived pollutants such as microplastics strongly demand technologies for waste plastic utilization. In this study, polyethylene terephthalate (PET) from waste plastic bottles was directly utilized to prepare a matrix of an adsorbent for cesium (Cs+) removal. The organic matrix of PET-derived oligomers obtained by aminolysis depolymerization was impregnated with bentonite clay and magnetite nanoparticles (Fe 3 O 4 NPs), playing the roles as a major adsorptive medium for Cs+ removal and as a functional component to primarily provide efficient separation of the hybrid adsorbent from aqueous system, respectively. The obtained hybrid composite microparticles were next tested as an adsorbent for the removal of Cs+ cation from aqueous solutions. The adsorption process was characterized by fast kinetics reaching ca. 60% of the equilibrium adsorption capacity within 5 min and the maximum adsorption capacity toward Cs+ was found to be 26.8 mg/g. The adsorption process was primarily dominated by the cationic exchange in bentonite, which was not significantly affected by the admixture of the competing mono- and divalent cations (Na+, K+, and Mg2+). The proposed approach here exploits the sustainable utilization scenario of plastic waste-derived material to template complex multifunctional nanocomposites that can find applications for pollution cleaning and environmental remediation. [Display omitted] • A novel method of waste PET conversion to a matrix for bentonite was proposed. • Microparticles were prepared by PET aminolysis and co-precipitation with bentonite. • Fe 3 O 4 NPs were utilized to confer the hybrid microparticles with magnetic property. • Application of hybrid magnetic microparticles for cesium removal was demonstrated. • Adsorption capacity of hybrid magnetic microparticles for cesium was ca. 26.8 mg/g. [ABSTRACT FROM AUTHOR]

The pervasive presence of plastics in the environment, particularly microplastics, has become a significant global challenge, demanding innovative solutions for their management and upcycling. While traditional methods including landfill and incineration face limitations in environmental impact, emerging technologies offer promising pathways for the conversion of plastics into valuable chemicals and fuels, operating under ambient conditions and often utilizing sustainable energy sources. Considering the current research progress in plastic upgrading, it is necessary to summarize the chemical upcycling of plastic waste. To this end, this review provides an overall examination of current and emerging methodologies for plastic treatment, including pyrolysis, hydrogenolysis, photocatalysis, and electrocatalysis. Existing knowledge gaps and future research directions are then proposed. Overall, this review highlights the potential of these novel plastic management approaches in aligning with the principles of a circular economy. [Display omitted] • Chemical upcycling of plastic provides a sustainable method for plastic waste management. • Pyrolysis and hydrogenolysis show promise in depolymerizing plastic but consuming large amounts of energy. • Photocatalysis and electrocatalysis are emerging technologies that leverage renewable energy sources for plastic upcycling. [ABSTRACT FROM AUTHOR]

Chemical upcycling of non-biodegradable polymers can shift the current linear plastic economy towards circular patterns. This work studies the environmental impacts of poly(ethylene terephthalate) (PET) upcycling given its extensive use in packaging, textile and automotive industries. A prospective gate-to-gate life cycle assessment is applied to five PET upcycling processes representative of common chemoselective depolymerization strategies. Laboratory-scale upcycling is scaled-up for processes depolymerizing 1 kg of post-consumer PET. With a global warming potential from 4.3 to 5.8 kg·CO 2 equiv. per kg of upcycled postconsumer PET, Glycolysis-PG using propylene glycol and a manganese acetate catalyst, Aminolysis and Hydrogenolysis processes bear the lowest global warming potential. On the contrary, the Glycolysis-EG process that uses ethylene glycol (EG) and a protic ionic salt catalyst has the largest global warming potential of 91.3 kg·CO 2 equiv. per kilo of PET. These differences are driven by variabilities in the energy and solvent consumption, and the presence of catalysts. Two sensitivity analyses focused on EG recirculation and ethylene carbonate production are performed to explore environmentally friendlier processes. Overall, this work highlights the environmental hotspots during postconsumer PET upcycling, guiding the implementation of sustainable approaches in polymer recycling. Environmental impacts of poly(ethylene terephthalate) upcycling via chemoselective depolymerization are quantified by prospective life cycle assessment to guide future sustainable circular polymer economy. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Achieved effective depolymerization of polyethylene under solvothermal liquefaction conditions. • Obtained 75% of polyethylene conversion with acetone as solvent at 350 °C. • Measured oil products HHV of 43.83 MJ/kg. • Hypothesized solvothermal liquefaction reactions to follow pyrolysis pathway of random scission. • Concluded solvation of polyethylene as responsible for lowing the liquefaction temperature. Depolymerization of polyethylene (PE) is one of the most challenging tasks in the chemical upcycling of PE-based plastic wastes because the disassociation of the stable carbon–carbon bonds in PE is only possible at a very high reaction temperature. The thermal liquefaction of PE cable plastic waste in a stainless-steel batch reactor was thoroughly evaluated in this study. The effect of different liquefaction methods (hydrothermal liquefaction (HTL), ionic liquids catalyzed HTL, and solvothermal liquefaction (STL)) on the yields of product fractions (oil products, solid residue, and gas) and the properties of the oil products were examined. At 350 °C and 90 min reaction duration, the conversion (%) of 75.43%, the oil yield of 39.33%, the energy recovery rate of 39.7%, the higher heating values (HHV) of 43.83 MJ/kg for the oil samples, and the lower boiling range molecular distribution were obtained by the solvothermal liquefaction method with acetone as a solvent. The HHV of the oil samples obtained in the STL method (43.28–43.83 MJ/kg) is comparable to that of gasoline (HHV − 43.4 MJ/kg). The contribution of the solvent to the depolymerization reaction was mainly the dissolution and dispersion of feedstock by solvation, therefore reducing thermal cracking temperature through enhanced mass and thermal energy transfer. In thermal liquefaction, solvent and feedstock had a low level of solvolysis reactions, so the depolymerization reaction mainly follows thermal cracking. The main reaction path is the random scission of PE molecules during heat treatment, with a low level of polymerization, cyclization, and radical recombination reactions, which occurred through the free radical mechanisms. This work has demonstrated the feasibility of a very promising technique for effective chemical upcycling of polyethylene-based plastics. [ABSTRACT FROM AUTHOR]

[Display omitted] • The background of the plastic waste treatments is summarized. • The nanocatalyzed upcycling of the plastics for a circular economy is reviewed. • Coordination chemistry aspects are emphasized in plastics depolymerization mechanisms. • Nanocatalyzed pyrolysis, solvolysis, hydrocracking and light induction are discussed. • Rational design of nanocatalysts and coordination environments are examined. Plastics are now essential components in our daily life, but they have also raised a waste crisis and environmental pollution issues. The traditional plastic waste treatments rely on high-energy input and are environmentally unfriendly. The emergence of nanocatalyzed chemical upcycling of plastic waste approaches, aiming to convert wastes to value-added chemicals, is encouraging and may enable a circular-plastics economy. Thus, in this Review, we first briefly summarize the background of the plastic waste treatments by introducing the most common plastic types and the traditional treatment methods. We then review the chemical upcycling of plastics in terms of nanocatalyzed pyrolysis, pyrolysis-gasification, solvolysis, hydrocracking and the light/electrochemical-induced processes from a historical account to recent achievements. Coordination chemistry aspects are emphasized in these processes, particularly in the plastics depolymerization mechanism. Emphasis is placed on highlighting the encouraging results recently obtained, especially on the rational design of nanocatalysts with tunable active metals, size, support, and coordination environments for improved catalytic performances. Indications towards further research and applications for value-added products synthesis are also proposed. In addition, some other emerging technologies for waste plastic treatments are introduced. Finally, perspectives for further developments towards a circular-plastic economy are highlighted. [ABSTRACT FROM AUTHOR]

Cover Feature: Versatile Chemical Recycling Strategies: Value-Added Chemicals from Polyester and Polycarbonate Waste (ChemSusChem 8/2022) Keywords: chemical upcycling; green chemistry; homogeneous catalysis; polycarbonates; polyesters EN chemical upcycling green chemistry homogeneous catalysis polycarbonates polyesters 1 1 1 04/26/22 20220422 NES 220422 B The Cover Feature b shows the chemical upcycling of various commercial plastics into value-added products, which include green solvents, chemical building blocks, and new materials. Chemical upcycling, green chemistry, homogeneous catalysis, polycarbonates, polyesters. [Extracted from the article]