Chemical Upcycling of Polyolefin Plastics Using Structurally Well-defined Catalysts

Upcycling polyolefins into value-added hydrocarbons via catalytic hydrogenolysis is challenging due to poor product selectivity, random C−C bond cleavage, and the formation of volatile alkanes. We have developed two isoreticular porous aluminum metal−organic framework (MOF) node-supported mononuclear ruthenium dihydride catalysts (DUT-5-RuH 2 and MIL-53-RuH 2 ), which are efficient in the hydrogenolysis of lowdensity polyethylene (LDPE) at 200 °C into a narrow distribution of liquid hydrocarbons (C8-C24). By systematic tuning of the pore sizes of the MOFs, high yields of desirable liquid alkanes were afforded with varying degrees of branching, achieving 80% selectivity. DUT-5-RuH 2 produced a C22-centered bell-shaped alkane distribution with a polyethylene conversion of 98%, while MIL-53-RuH 2 , being selective for shorter alkanes, produced a C9-centered bell-shaped alkane distribution. Based on our spectroscopic and theoretical studies, the high catalytic activity and selectivity of these MOF catalysts are primarily attributed to the stabilization of single-site mono-RuH 2 species at the MOF's nodes via active-site isolation and the confinement of the active catalytic species within porous MOFs. Theoretical calculations suggest that RuH 2 -mediated polyolefin C−C bond cleavage primarily occurs via turnover-limiting σ-bond metathesis. This study underscores the significance of MOFs in the rational design of heterogeneous catalysts for the efficient upcycling of plastic waste.

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Selective Upcycling of Polyolefins into High-Value Nitrogenated Chemicals

Zhao,

Hu,

Sun

et al. 2024

J. Am. Chem. Soc.

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The selective upcycling of polyolefins to create products of increased value has emerged as an innovative approach to carbon resource stewardship, drawing significant scientific and industrial interest. Although recent advancements in recycling technology have facilitated the direct conversion of polyolefins to hydrocarbons or oxygenated compounds, the synthesis of nitrogenated compounds from such waste polyolefins has not yet been disclosed. Herein, we demonstrate a novel approach for the upcycling of waste polyolefins by efficiently transforming a range of postconsumer plastic products into nitriles and amides. This process leverages the catalytic properties of manganese dioxide in combination with an inexpensive nitrogen source, urea, to make it both practical and economically viable. Our approach not only opens new avenues for the creation of nitrogenated chemicals from polyolefin waste but also underscores the critical importance of recycling and valorizing carbon resources originally derived from fossil fuels. This study provides a new upcycling strategy for the sustainable conversion of waste polyolefins.

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Chemical Upcycling of Polyolefin Plastics Using Structurally Well-defined Catalysts

Cited by 5 publications

References 66 publications

Chemical Innovations in Polymer Upcycling: Beyond Traditional Recycling

Chemical Innovations in Polymer Upcycling: Beyond Traditional Recycling

Hydrogenolysis of Polyethylene by Metal–Organic Framework Confined Single-Site Ruthenium Catalysts

Selective Upcycling of Polyolefins into High-Value Nitrogenated Chemicals

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