Chemical Upcycling of Poly(bisphenol A carbonate) to Diglycerol Dicarbonate: A Strategy to Repurpose Polycarbonates to Polyurethanes Using Biobased Diglycerol

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.

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.

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.

The chemical upcycling of waste plastics into high-value-added products such as monomers, fuels, or fine chemicals represents a promising strategy for mitigating the adverse effects of massive end-of-life plastics. Poly(bisphenol A carbonate) (BPA-PC) stands out as a notable engineering plastic due to its exceptional overall performance; however, its durability and potential environmental toxicity make its recycling imperative. Although a lot of reviews about plastic degradation have been done before our review, the progress for plastic degradation needs to be constantly updated and summarized due to the rapid development of this field. Meanwhile, BPA-PC, as an important notable engineering plastic, previous reviews only focused on its depolymerization into monomers and missed their further conversion into final chemicals. which In this concise review, we summarize recent developments in the chemical upcycling of BPA-PC to valuable chemicals, emphasizing the role of various catalysts and reagents. Some of the most utilized chemical upcycling strategies such as alcoholysis, aminolysis and upcycling of BPA-PC in “polymer-to-polymer” format to reproduce new polymers are elucidated in detail. Finally, we provide insights into the future prospects of chemical upcycling for waste BPA-PC.

Enabling resource circularity through thermo-catalytic and solvent-based conversion of waste plastics

Chemical upcycling is an attractive platform for converting plastic waste into valuable products. Here, a tandem deconstruction-catalysis route was developed for upcycling polypropylene (PP). A ternary-active NiO-NiAl2O4-Al2O3 nanocomposite was innovatively synthesized, with the NiO/NiAl2O4 particle size lowering to ca. 5 nm, affording abundant active sites. Importantly, it demonstrated excellent reusability, maintaining high catalytic activity over 30 cycles with the highest liquid yield of 63.33 wt %, primarily composed of branched olefins. Particularly, it was capable of effectively upcycling real-world PP medical operating coats, achieving a narrower carbon number distribution with exceptionally high carbon selectivity of 90.18 mol % for gasoline (C4-C12)-range hydrocarbons, respectively. Additionally, in situ Fourier transform infrared spectroscopy characterization revealed that the ternary-active nanocomposite facilitated the activation and pre-cracking of PP chains into shorter, unsaturated oligomers, which were subsequently converted into branched olefins and aromatics. In brief, this study proposed a promising solution using a ternary-active nanocomposite to effectively upcycle PP waste.

Depolymerization is a promising solution to address the escalating global plastic waste crisis, as a key enabler for emerging technologies in chemical upcycling and closed‐loop recycling of plastics. By virtue of their unparalleled bottom‐up designability for structural control, stability, reactivity, and compatibility with catalytically‐active metal nanoparticles and enzymes, MOFs have enormous potential as an emerging class of porous heterogeneous catalysts for plastics depolymerization. Herein, we highlight key considerations and advances in MOF catalyst development and design for a range of depolymerization reactions, including alcoholysis, hydrogenolysis, pyrolysis, photocatalytic oxidation, and enzymatic hydrolysis. Other than enabling MOFs to efficiently depolymerize the most abundant plastics in production today, including those with unreacted C─C backbones (e.g., polyolefins) and polymers with cleavable backbone linkages (e.g., polyesters), their versatility also extends to emerging applications in microplastic capture and degradation from wastewater. These unique properties of MOFs position them as potentially scalable and reusable heterogeneous catalysts that can complement existing inorganic catalysts for practical depolymerization.

Unlocking opportunities: Supported metal catalysts for the chemical upcycling of waste plastics

From plastic waste to potential wealth: Upcycling technologies, process synthesis, assessment and optimization

Luminescent carbon dots (CDs), as an emerging material class, have been actively investigated for applications in bioimaging, photocatalysis, and optoelectronic devices. Polymer materials have exhibited great potential as candidates for the preparation of CDs due to the high carbon percentage in their chemical structure and relative abundance. More importantly, chemical upcycling provides an economic approach to process polymer waste. In this article, we review synthetic routes and optical properties of CDs derived from different polymer sources, including polyethylene, polypropylene, mixed polyolefins, polystyrene, polyurethane, polyethylene terephthalate, polyethylene glycol, polylactide, polyacrylamide and polymers derived from natural resources. Applications based on the luminescent properties of these polymer-derived CDs are also briefly discussed. Though most of the current polymer-derived CDs show inferior photoluminescence quantum yields to those of small-molecule-derived CDs, there are pathways to improve the performance of polymer-derived CDs by adjusting the synthetic conditions and incorporating additives or dopants.

Waste to energy: Trending key challenges and current technologies in waste plastic management

Depolymerization is a promising solution to address the escalating global plastic waste crisis, as a key enabler for emerging technologies in chemical upcycling and closed-loop recycling of plastics. By virtue of their unparalleled bottom-up designability for structural control, stability, reactivity, and compatibility with catalytically-active metal nanoparticles and enzymes, MOFs have enormous potential as an emerging class of porous heterogeneous catalysts for plastics depolymerization. Herein, we highlight key considerations and advances in MOF catalyst development and design for a range of depolymerization reactions, including alcoholysis, hydrogenolysis, pyrolysis, photocatalytic oxidation, and enzymatic hydrolysis. Other than enabling MOFs to efficiently depolymerize the most abundant plastics in production today, including those with unreacted C─C backbones (e.g., polyolefins) and polymers with cleavable backbone linkages (e.g., polyesters), their versatility also extends to emerging applications in microplastic capture and degradation from wastewater. These unique properties of MOFs position them as potentially scalable and reusable heterogeneous catalysts that can complement existing inorganic catalysts for practical depolymerization.

With the increasing consumption of single-use plastics, a large number of petrochemical resources are used as raw materials, and hundreds of thousands of tons of plastic waste are produced every year. Although there are lots of methods that have been developed to solve this issue by recycling plastic waste, none of them can recover the value of the waste in an efficient way that is less economical cost and less harmful to the environment. Polyethylene terephthalate (PET) is one of the most widely produced single-use polymers. It is challenging to recover the value through mechanical recycling due to the degrading of properties during reprocessing. Chemical upcycling/recycling is an alternative to convert the polymer back to the monomer with less environmental effect, which has lower energy demand. Hydrolysis is one of the common methods in chemical upcycling; it can convert PET waste into value-added materials such as H2 fuel. This paper mainly focuses on the method that converts PET to value-added chemicals through hydrolysis in recent years, so as to offer some references for future researches.

Plastic waste accumulation is one of the most pressing environmental challenges of the 21st century, owing to the widespread use of synthetic polymers and the limitations of conventional recycling methods. Among available strategies, chemical upcycling via depolymerization has emerged as a promising circular approach that converts plastic waste back into valuable monomers and chemical feedstocks. This article provides an in-depth narrative review of recent progress in the upcycling of major plastic types such as PET, PU, PS, and engineering plastics through thermal, chemical, catalytic, biological, and mechanochemical depolymerization methods. Each method is critically assessed in terms of efficiency, scalability, energy input, and environmental impact. Special attention is given to innovative catalyst systems, such as microsized MgO/SiO2 and Co/CaO composites, and emerging enzymatic systems like engineered PETases and whole-cell biocatalysts that enable low-temperature, selective depolymerization. Furthermore, the conversion pathways of depolymerized products into high-purity monomers such as BHET, TPA, vanillin, and bisphenols are discussed with supporting case studies. The review also examines life cycle assessment (LCA) data, techno-economic analyses, and policy frameworks supporting the adoption of depolymerization-based recycling systems. Collectively, this work outlines the technical viability and sustainability benefits of depolymerization as a core pillar of plastic circularity and monomer recovery, offering a path forward for high-value material recirculation and waste minimization.

Chemical upcycling that catalyzes waste plastics back to high‐purity chemicals holds great promise in end‐of‐life plastics valorization. One of the main challenges in this process is the thermodynamic limitations imposed by the high intrinsic entropy of polymer chains, which makes their adsorption on catalysts unfavorable and the transition state unstable. Here, we overcome this challenge by inducing the catalytic reaction inside mesoporous channels, which possess a strong confined ability to polymer chains, allowing for stabilization of the transition state. This approach involves the synthesis of p‐Ru/SBA catalysts, in which Ru nanoparticles are uniformly distributed within the channels of an SBA‐15 support, using a precise impregnation method. The unique design of the p‐Ru/SBA catalyst has demonstrated significant improvements in catalytic performance for the conversion of polyethylene into high‐value liquid fuels, particularly diesel. The catalyst achieved a high solid conversion rate of 1106 g ⋅ gRu−1 ⋅ h−1 at 230 °C. Comparatively, this catalytic activity is 4.9 times higher than that of a control catalyst, Ru/SiO2, and 14.0 times higher than that of a commercial catalyst, Ru/C, at 240 °C. This remarkable catalytic activity opens up immense opportunities for the chemical upcycling of waste plastics.