Conversion Of Polyethylene Terephthalate Research Articles

Selective Oxidation of Polyesters via PdCu-TiO2 Photocatalysts in Flow.

Catalytic upcycling of plastic wastes offers a sustainable circular economy. Selective conversion of the most widely used polyester, polyethylene terephthalate (PET), under ambient conditions is practically attractive because of low energy consumption and carbon footprint. Here, we report selective, aerobic conversion of PET in a flow reactor using TiO2 photocatalyst modified with atomic Pd and metallic PdCu (Pd1Cu0.4-TiO2) under ambient conditions. We demonstrate that atomically synergistic Pd1Cu0.4-TiO2 exhibits a formate evolution of 4707 μmol g-1 h-1 with a selectivity of 92.3% together with trace COx released. Importantly, we show that this corresponds to 10-103 times greater activity than reported photocatalytic systems. We confirm that synergy between atomic Pd and metallic PdCu boosts directional charge transfer and oxygen-induced C-C cleavage and inhibits product decomposition. We conclude that photocatalytic waste plastic-to-chemical conversion is sustainable via targeted engineering of atomically synergistic catalysts and reaction systems.

Synergistic effect of diatomaceous earth as a catalyst and terephthalic acid as a co-catalyst on chemical recycling of polyethylene terephthalate via hydrolysis

Polyethylene terephthalate (PET) is one of the most useful commodity polymers that have been used extensively in packaging and textile industry and hence it has become a concerning waste. In this work, diatomaceous earth (DE), terephthalic acid (TPA) and distilled water were used to hydrolyze PET waste from drinking water bottles into TPA and ethylene glycol (EG). TPA can be used as one of the monomers for the synthesis of PET or other industrial applications such as for the synthesis of alkyd resins. Here DE was used as a solid catalyst which can be separated by a simple filtration after the TPA removal, in contrast to the majority of earlier efforts, which used aqueous acid or base catalysts that are difficult to separate. Additionally, commercial TPA, which is used as co-catalyst, can easily be substituted by produced TPA from the PET hydrolysis. The conversion of PET and the yield of TPA, using 5.0 wt % of DE and 3.0 wt % of commercial TPA with a PET:H2O mass ratio of 1.0:3.0, at 185 °C and 11.2 bar was 100 % and 95.40 % respectively, obtained in 2.5 h. TPA product was isolated from the reaction mixture by basic wash and subsequent neutralization and it was characterized by infrared spectroscopy, nuclear magnetic resonance, differential scanning calorimetry, X-ray diffraction and thermogravimetric analysis. The effects of reaction parameters such as reaction temperature, reaction time, mass ratio of PET:H2O and the catalysts loading on the yield of TPA were studied. The optimized reaction was repeated over seven consecutive reaction cycles using recovered DE to further demonstrate the effectiveness of reused DE and it was found that the outcomes were unaltered. Due to DE's affordability and accessibility, this reaction is a green and convenient way to handle the staggering accumulation of PET waste.

Effect of pyrolysis operating conditions on the catalytic co‐pyrolysis of low‐density polyethylene and polyethylene terephthalate with zeolite catalysts

AbstractIn this study, the catalytic (co‐)pyrolysis of low‐density polyethylene (LDPE) and polyethylene terephthalate (PET) with HZSM‐5 and HY zeolite catalysts was conducted in a micro‐pyrolysis reactor coupled to a two‐dimensional gas chromatography system. Pyrolysis operating conditions, such as the pyrolysis temperature, the catalyst to feedstock (CF) ratio, and the LDPE:PET ratio, were varied. It was found that for the co‐pyrolysis of LDPE and PET, HZSM‐5 led to higher yields of C2‐C4 olefins and monoaromatic products. Lower CF ratios increased the yield of C2‐C4 olefins for LDPE pyrolysis, but decreased benzene yield for PET pyrolysis, concomitant with an increased yield in benzoic acid. A lower temperature of 400°C which was sufficient for the pyrolysis of LDPE, led to incomplete conversion of PET. Surface response diagrams were used to visualize the impact of the various pyrolysis operating conditions on the yield of C2‐C4 olefins and BTEX, which serve as target products for the circular economy.

Selective recovery of para-xylene from polyethylene terephthalate plastic

The conversion of polyethylene terephthalate (PET) plastic into low-boiling monomers like para-xylene (PX) that can be purified easier with lower energy consumption represents a promising strategy for circular economy that seamlessly integrating into current prevailing high-quality PET production chain. Herein, a selective bimetallic RuFe catalyst was successfully fabricated for hydrodeoxygenation (HDO) of dimethyl terephthalate (DMT) (a model compound of PET) and PET plastics to PX with yield as high as 88.9 % and 82.6 %, respectively, comparable to state-of-the-art examples. H2-TPR and EXAFS combined with benchmark test over model catalysts confirmed that small Ru clusters and Ru-Nx coordination are responsible for the high aromatics selectivity, on which vertical adsorption of carbonyl group (CO) is preferred. This study not only shows a promising PX-based PET recycling route, the highly selective C–O bond cleavage on Ru catalyst and corresponding structure-selectivity relationship also guide the catalyst design for other value-added biomass-based HDO reactions.

Boosting the Initial Coulombic Efficiency of Sustainable Hard Carbon Derived from Polyethylene Terephthalate with Cyclopentyl Methyl Ether As a Co-Solvent for Wide-Temperature Sodium-Ion Batteries

Upcycling plastic waste into value-added products helps to generate cost-effective and sustainable resources towards a circular materials economy and safer ecosystem. The conversion of polyethylene terephthalate (PET) municipal waste via the carbonization process into hard carbon (HC) delivers a high-reversible capacity, low-cost, sustainable anode material for sodium-ion batteries (SIBs). However, the low initial Coulombic efficiency (ICE) is a significant challenge of the HC anode, which should be optimized by electrolyte and interfacial chemistry.1 In conventional carbonate esters-based electrolytes, ethylene carbonate (EC) forms an organic-rich thick SEI layer, soluble on cycling, limiting the cyclic stability. The low-temperature performance is also a significant concern in achieving high capacity, long cyclability, and ICE.2 Herein, HC derived via single-step carbonization at 1000℃ exhibits larger interlayer spacing of 0.379 nm, low surface area (~205 m2g-1), and unique slit-shaped pores with 84% mesoporosity in the structure. PET-HC exhibits a high reversible capacity of 337 mAh g-1 with ICE of just 66%, using EC-PC-based electrolyte. EC-free cyclopentyl methyl ether (CPME) was used due to its weakly solvating and wide temperature solvent.3 CPME-PC-based electrolytes significantly enhanced the ICE value to 74.5% and reversible capacity to 356 mAh g-1 with superior cycling of 91% after 100 cycles at 0.1C rate. The inorganic-rich SEI layer for CPME-PC-based electrolytes results in a thin SEI that improves the ICE and cyclic stability of the anode. The low-temperature performance (up to -20°C) for CPME-PC-based electrolytes showed ~30% added capacity compared to EC-PC-based electrolytes. This work provided an eco-friendly approach to developing hard carbons from plastic trash and offered an effective strategy to replace EC with CPME for low-temperature sodium storage applications. References Shen, L., Shi, S., Roy, S., Yin, X., Liu, W., Zhao, Y., Adv. Funct. Mater. 2021, 31, 2006066. Ramasamy, H. V., Kim, S., Adams, E. J., Rao, H. & Pol, V. G. Chem. Commun. 2022, 58, 5124–5127.Zhang, H., Zeng, Z., Ma, F., Wu, Q., Wang, X., Cheng, S., Xie, J., Angew. Chem. 2023, e202300771. Figure 1

Valorization of Waste Plastics into Nanostructured Materials for LI-ION Storage Application

Every year, several million tons of plastics are wasted, resulting in significant environmental pollution. Polyethylene terephthalate (PET) is one of the most commonly used plastics, with approximately 400 billion drink bottles produced annually. The widespread availability and environmental concerns associated with the non-natural degradability of PET waste necessitate the development of clean, efficient, and low-cost recycling methods or valorization into high-value materials. In this presentation, the molten salt conversion of waste PET into carbonaceous nanostructures is discussed as a facile, scalable, and fast method for valorizing PET waste. For instance, this molten salt process can result in the preparation of terephthalic acid embedded with tin dioxide nanocrystals. The resulting nanocomposite material shows interesting performance as anode of high-performance lithium-ion batteries. The structural, morphological and electrochemical performance of the terephthalic acid- tin dioxide are discussed in this presentation.

Computational design of highly efficient thermostable MHET hydrolases and dual enzyme system for PET recycling

Recently developed enzymes for the depolymerization of polyethylene terephthalate (PET) such as FAST-PETase and LCC-ICCG are inhibited by the intermediate PET product mono(2-hydroxyethyl) terephthalate (MHET). Consequently, the conversion of PET enzymatically into its constituent monomers terephthalic acid (TPA) and ethylene glycol (EG) is inefficient. In this study, a protein scaffold (1TQH) corresponding to a thermophilic carboxylesterase (Est30) was selected from the structural database and redesigned in silico. Among designs, a double variant KL-MHETase (I171K/G130L) with a similar protein melting temperature (67.58 °C) to that of the PET hydrolase FAST-PETase (67.80 °C) exhibited a 67-fold higher activity for MHET hydrolysis than FAST-PETase. A fused dual enzyme system comprising KL-MHETase and FAST-PETase exhibited a 2.6-fold faster PET depolymerization rate than FAST-PETase alone. Synergy increased the yield of TPA by 1.64 fold, and its purity in the released aromatic products reached 99.5%. In large reaction systems with 100 g/L substrate concentrations, the dual enzyme system KL36F achieved over 90% PET depolymerization into monomers, demonstrating its potential applicability in the industrial recycling of PET plastics. Therefore, a dual enzyme system can greatly reduce the reaction and separation cost for sustainable enzymatic PET recycling.

Conversion of polyethylene terephthalate (PET) plastic particles in a microwave-assisted heating reactor

Abstract With the rapid economic development, PET (polyethylene terephthalate) plastic is widely used in various fields, i.e., clothing, food, housing and transportation. However, PET has a very strong chemical inertia, which makes it difficult to be degraded by microorganisms, thereby occupying a lot of space. Therefore, the recycling of waste PET has become one of the most important topics of environmental protection. Glycolysis requires the most mild and safe reaction environment among chemical recycling methods, and the ethylene glycol used in the reaction can be reused. Using glycolysis to recycle PET undoubtedly conforms to the green and sustainable concept, and glycolysis recycling is undoubtedly a low-cost, low-consumption and low-harm path for PET recycling. The heating and glycolysis characteristics of microwave-assisted PET glycolysis, and the energy analysis of glycolysis were studied. The aim was to produce BHET (bis(2-hydroxyethyl) terephthalate) as the target product from PET waste. In this study, the effects of reaction temperature, reaction time, and PET particle size on the performances of PET conversion rate, oligomeric BHET yield, and BHET yield were examined, and the energy efficiency and recovery efficiency also were presented. The results showed that the optimal conditions for microwave-assisted PET glycolysis were reaction temperature of 180 °C, reaction time of 30 min, and PET particle size of 75 μm, and the maximum PET conversion rate was 66.71 ± 9.71 wt%, the maximum yield of BHET was 48.08 ± 0.68 wt% and the maximum BHET yield was 19.83 ± 5.40 wt%. The energy efficiency and recovery efficiency were 11.88 % and 17.89 %, respectively.

Insight the influence of the catalyst basicity on glycolysis behavior of Polyethylene terephthalate (PET)

Although polyethylene terephthalate (PET) is one of the most prevalent plastics, a cumulative disposal of PET waste has caused adverse effects on both economy and environment. Catalytic glycolysis of PET waste has emerged as a prevalent and sustainable pathway to address this problem. Due to the limitations of recovery and recycling, the catalytic development trend for PET glycolysis has recently changed from homogenous to heterogeneous designs. Herein, metal oxides with different basicity, including calcium, cerium, and cobalt, were supported on alumina and first employed in the glycolysis process of waste PET plastic. A plausible mechanism is proposed and reveals the correlation between the basicity of as-prepared catalyst and glycolysis performances. Among these catalysts, 10%Ce/Al2O3 exhibited a complete conversion of waste PET with the highest selectivity to the main product BHET. There is no significant drop in catalytic activity after five consecutive runs. Furthermore, the excellent quality of the monomer product BHET was confirmed via different analysis techniques. This work has contributed to a promising notion for engineering efficient heterogeneous catalysts of PET recycling technology.

Ruthenium/TiO2 -Catalyzed Hydrogenolysis of Polyethylene Terephthalate: Reaction Pathways Dominated by Coordination Environment.

Polyethylene terephthalate (PET) hydrogenolysis can produce benzene, toluene, and xylene (BTX), where the selectivity control is challenging. We report a reaction pathway dictated by the Ru coordination environment by examining the binding geometries of adsorbates on differently coordinated Ru centers and their evolution during PET hydrogenolysis. A BTX yield of 77 % was obtained using a Ru/TiO2 with a Ru coordination number of ca. 5.0 where edge/corner sites are dominant, while more gas and saturated products were formed for Ru/TiO2 containing primarily terrace sites. Density functional theory and isotopic labelling revealed that under-coordinated Ru edge sites favor "upright" adsorption of aromatic adsorbates while well-coordinated Ru sites favor "flat-lying" adsorption, where the former mitigates ring hydrogenation and opening. This study demonstrates that reaction pathways can be directed through controlled reactant/intermediate binding via tuning of the Ru coordination environment for efficient conversion of PET to BTX.

Efficient H2 Production from PET Plastic Wastes over Mesoporous Carbon-Supported Ru-ZnO Catalysts in a Mild Pure-Water System

The massive consumption of plastic is posing severe pollution-related challenges globally. As the most abundant polyester plastic, polyethylene terephthalate (PET) waste represents a largely untapped resource for generating chemicals and fuels. However, the current widespread use of alkali/organic solvents and the complex processing of PET reduce its environmental sustainability. Herein, a novel and simple one-pot strategy was first reported for the catalytic conversion of PET into H2 fuel and terephthalic acid in a pure-water system under mild conditions. A high H2 yield of 19.97 mol/kgPET and carbon conversion efficiency of 97.22% were obtained for the Ru-5ZnO/mesoporous carbon (MEC) catalyst at a low temperature of 250 °C. This process proceeds through tandem catalytic reactions with an initial PET depolymerization step, followed by in situ aqueous phase reforming (APR) of ethylene glycol of Ru. Remarkably, ZnO inhibited the deactivation of Ru/MEC in the PET depolymerization stage, causing an increase in H2 production from the in situ APR stage. Importantly, this strategy was successfully applied to four types of real-world PET waste and their mixtures, demonstrating that it has considerable potential in practical applications and provides a sustainable and clean solution to the plastic waste problem.

Depolymerization of polyethylene terephthalate with glycol under comparatively mild conditions

The depolymerization of polyethylene terephthalate (PET) can proceed by using ethylene glycol (EG) as an alcoholysis solvent. However, high reaction temperature (≥180℃) of glycolysis process requires high energy consumption, and unfortunately results in yellowing of monomer product, i.e., bis(2-hydroxyethyl) terephthalate (BHET), limiting the production of high-quality and colorless recycled PET (rPET). To address this problem, a strategy involving acetonitrile as cosolvent was applied to decrease glycolysis temperature to 90℃ or even lower, and solvents as well as catalyst can be recycled and reused. The glycolysis of PET is hard to proceed at 90℃. However, the swelling effect of acetonitrile caused cracks and defects on the surface of PET, which promoted the depolymerization of PET and led to an S-shaped reaction curve. Besides, adding acetonitrile could significantly accelerate the degradation of oligomers into BHET. Under the optimal reaction conditions, the conversion of PET and yield of BHET could reach 96% and 90%, respectively.

Copper catalyzed co‐pyrolysis of polyethylene terephthalate with low and high density polyethylene for liquid fuel production

AbstractBACKGROUNDMunicipal waste contains low density polyethylene (LDPE), high density polyethylene (HDPE), and polyethylene terephthalate (PET) in enormous amount. As these plastics are non‐biodegradable and pose serious threats to the environment, efforts have been made towards their safe disposal with energy recovery and value added chemicals by subjecting them to heat under oxygen deficient conditions. This study deals with the co‐pyrolysis of the three types of waste polymers, with special focus on the conversion of PET into liquid fuel by its interaction with the other two polymers.ResultsThe individual pyrolysis of LDPE and HDPE produced pyrolysis oil, whereas PET produced only wax. The co‐pyrolysis of the three polymers with different mixing ratios showed that PET hindered oil formation and increasing its amount more than 20 wt% in the polymer mixture resulted in wax formation. The thermal process produced 8 wt% pyrolysis oil, 32.3 wt% wax, 39.7 wt% pyro‐gases and 20 wt% coke while the catalytic process with copper catalyst produced 32.5 wt% pyrolysis oil, 3 wt% wax, 46.5 wt% pyro‐gases, and 18 wt% coke under optimum conditions.ConclusionThe thermal pyrolysis oil contained long chain paraffins as major components, while short chain isoparaffin and naphthenes were predominant in the catalytic pyrolysis oil owing to which marked differences were observed in the physicochemical properties of both oils. The fractionally distilled fractions of catalytic pyrolysis oil in gasoline, kerosene, and diesel range showed profound similarities with standard fuels in terms of fuel properties particularly the gasoline range fraction. © 2022 Society of Chemical Industry (SCI).

Chemical conversion of waste PET to valued-added bis(2-hydroxyethyl) terephthalamide through aminolysis

Polyethylene terephthalate (PET) refers to a widely used thermoplastic polymer that is difficult to degrade naturally. Therefore, large amounts of waste PET need to be recycled. In this study, to achieve a green and efficient method to degrade and recycle waste PET for new functional chemicals, PET waste was first swelled with acetic acid. Then, it was degraded under atmospheric pressure at 70 °C for 4 h using ethanolamine as solvent. The degradation efficiency of PET was higher than conventional methods because of the swelling-induced pores caused by the acetic acid. The aminolysis product bis(2-hydroxyethyl) terephthalamide was confirmed by Fourier transform infrared and nuclear magnetic resonance characterization methods and could be readily separated and recovered from the solvent. Finally, the degradation mechanism was discussed. This research provides a feasible and efficient approach to realize the recycling of PET with high value.

Ultrafast 99% Polyethylene terephthalate depolymerization into value added monomers using sequential glycolysis-hydrolysis under microwave irradiation

Effective and efficient hybrid depolymerisation technologies are emerging as high potential sustainable routes with considerable benefits over conventional recycling methods for the achievement of circular economies for plastics. Herein, combined green and fast glycolysis-hydrolysis depolymerization of polyethylene terephthalate (PET) was carried out under microwave irradiation (MW) with excellent efficiencies. In MW assisted glycolysis of PET, the catalytic activity of two deep eutectic solvents (DES) based on (choline chloride-urea (DES 1)) and (choline chloride-thiourea (DES 2)) was evaluated and compared. Optimised glycolysis conditions were determined using Box Behnken Design (BBD) to attain maximum weight loss of PET, low crystallinity and increased carbonyl index of residual PET. DES volume of 4 mL, 5.5–6 mL of ethylene glycol, and 0.5 min MW irradiation time resulted in a prominent rise in PET weight loss and carbonyl index of residual PET. DES 2 showed an improved catalytic activity than that of DES 1 which is associated to its stronger interaction with EG and PET polymer chains during the course of the reaction. Residual PET obtained post glycolysis reaction was further depolymerized using MW assisted hydrolysis in the presence of weakly basic Na2CO3 and EG. Within 3-minute, the proposed sequential depolymerization technologies facilitated ≈99% conversion of PET to terephthalic acid (TPA), monohydroxyethyl terephthalate (MHET), and bis (2-hydroxyethyl) terephthalate (BHET) monomers produced at a yield of 62.79–80.66%, 17.22–34.79% and 0.54–0.59% respectively. Application on post-consumer PET sample also revealed very satisfactory results with 96.77–98.25% PET conversion and 60.98–78.10% yield of TPA.

Poly(ionic liquid)s as efficient and recyclable catalysts for methanolysis of PET

The methanolysis of polyethylene terephthalate (PET) was investigated using poly(ionic liquid)s (PILs) synthesized with 1-vinyl-3-ethylimidazole acetates ([VEIm]Ac) and acrylic acid metal salts, and the activities of the PILs were screened. The effects of reaction temperature, reaction time, methanol amount, catalyst amount and PET sources on the methanolysis of PET were investigated using the optimized catalyst PIL-Zn2+. Under the optimal conditions the conversion of PET was 100% and the yield of dimethyl terephthalate (DMT) was 89.1%. In addition, the catalyst has very good applicability for methanolysis of different PET raw materials. More importantly, the PIL-Zn2+ catalyst could be recycled by simple filtration after the reaction, and could be reused six times without significant decrease in PET conversion and DMT yield. The catalysts were analyzed by TGA, FT-IR, XRD and ICP before and after recycling, the results showed no change in the structure of the catalyst, reflecting the good stability of the catalyst. The reaction kinetics of PIL-Zn2+ was first-order with an activation energy of 107.6 kJ/mol. This work mainly provides a way to design efficient, stable and recyclable catalysts for PET methanolysis.

Reprocessing of 3D printing filament’s fragment by hydrolysis and recycling into the formation of bioplastic

Currently, additive manufacturing become an expanding industry which committing high demand of plastic. Consequently, plastic waste generated will be increased exponentially. Polylactic acid (PLA) and polyethylene terephthalate (PET) are extensively used polymer as the filament for 3D printing. Therefore, the reprocessing of the fragments is necessary to reduce the plastic pollution. This study the aims to investigate the conversion of PET to terephthalic acid (TPA) and its conversion breakthrough via caustic soda hydrolysis. Meanwhile, the effect of PLA dissolution and its integration with glycerol to produced bioplastic was investigated. Fragment of PET was undergone hydrolysis process at different time and the conversion rate showed increment as prolong reaction time. TPA yield produced follow the same trend of PET conversion. FTIR analysis proved the formation of TPA after the hydrolysis process due to the formation of O–H and C–H which corresponding to the formation of carboxylic acid and ethylene glycol of TPA. Concurrently, PLA was dissolved in chloroform at different time and mixed with glycerol which acts as plasticizer to form PLA/glycerol plastic. It was found that the longer dissolution time, the higher the percentage of PLA dissolved. From FTIR analysis, the functional group of PLA has changed indicated that the reaction between dissolved PLA and glycerol has been taken placed. The results indicate that PET degradation can occur at low cost and on this basis. Ergo, this formation of valuable products from waste polymers can be an alternative method in promoting reduced waste generation.

Cover Feature: Emerging Strategies in Polyethylene Terephthalate Hydrolase Research for Biorecycling (ChemSusChem 19/2021)

The Cover Feature shows the current focus on the strategies requisite for biorecycling of polyethylene terephthalate (PET). The first strategy is improvement of PET hydrolase, which should be thermostable at over 70 °C and of high conversion rate to produce terephthalic acid by a single enzyme. Another strategy is conversion of waste PET to more degradable forms in an economical way. More information can be found in the Minireview by F. Kawai.

Hydrodynamic synthesis of Fe2O3@MoS2 0D/2D-nanocomposite material and its application as a catalyst in the glycolysis of polyethylene terephthalate.

We report a fast and simple synthesis of Fe2O3@MoS2 0D/2D-nanocomposite material using a Taylor–Couette flow reactor. A Taylor–Couette flow with high shear stress and mixing characteristics was used for fluid dynamic exfoliation of MoS2 and deposition of uniform Fe2O3 nanoparticles, resulting in a Fe2O3@MoS2 in the form of 0D/2D-nanocomposite material. Using Taylor–Couette flow reactor, we could synthesize Fe2O3@MoS2 0D/2D-nanocomposite material at a rate higher than 1000 mg h−1 which is much higher than previously reported production rate of 0.2–116.7 mg h−1. The synthesis of Fe2O3@MoS2 nanocomposite was achieved in an aqueous solution without thermal or organic solvent treatment. Exfoliated MoS2 nanosheets show an average thickness of 2.6 ± 2.3 nm (<6 layers) and a lateral size of 490 ± 494 nm. Fe2O3 nanoparticles have an average size of 7.4 ± 3.0 nm. Fe2O3 nanoparticles on chemically and thermally stable MoS2 nanosheets show catalytic activity in the glycolysis of polyethylene terephthalate (PET). High conversion of PET (97%) and a high yield (90%) for bis(hydroxyethyl) terephthalate (BHET) were achieved in a reaction time of 3 h at the reaction temperature of 225 °C.

Synthesis of two-dimensional holey MnO2/graphene oxide nanosheets with high catalytic performance for the glycolysis of poly(ethylene terephthalate)

Two-dimensional (2D) materials have been extensively studied as promising heterogeneous catalysts because of their high surface area, outstanding mechanical strength, and excellent chemical and thermal stability. Herein, we report an efficient and simple two-step strategy for the synthesis of 2D holey and ultrathin MnO2/graphene oxide nanosheets. As a 2D nanoporous support, holey graphene oxide (HGO) nanosheets are prepared by an oxidative etching method. The uniform and conformal deposition of MnO2 onto the HGO surface is performed by a solution-based self-limiting redox reaction, resulting in nanoporous MnO2/HGO nanosheets with a high surface area. The resulting MnO2/HGO shows outstanding catalytic performance for the glycolysis of polyethylene terephthalate (PET). A high conversion of PET (100%) and a high yield of a bis(hydroxyethyl) terephthalate (BHET) are achieved within a short reaction time of 10 min at a reaction temperature of 200 °C. Furthermore, the MnO2/HGO catalyst shows excellent recyclability for the glycolysis of PET; a BHET yield of 100% is obtained after 5 cycles.