Addressing the challenge of waste plastics treatments, the scientific community has been pursuing innovative solutions. Recently, Peking University researchers led by Ma Ding from College of Chemistry and Molecular Engineering, in collaboration with Xu Shutao from Dalian Institute of Chemical Physics, Chinese Academy of Sciences, uncovered how complex plastic mixtures can be utilized based on the differences in the physical and chemical properties of the components with the aids of NMR technique and catalytic approaches. This work provides a new treatment strategy for recovering real-life plastics and maximizing their potential as raw materials. Their findings, entitled "In-line NMR Guided Orthogonal Transformation of Real-life Plastics," were published in Nature on June 25, 2025.
Why it matters:
The global accumulation of plastic waste poses a serious threat to wildlife and ecosystems. Chemical recycling and upcycling technologies offers a promising solution by transforming waste plastics into valuable products, while currently most of them primarily handle single components or polymers with a same structural characteristic. However, efficient recycling of plastic mixtures remains challenging due to their complex composition and structural heterogeneity. However, there is still a lack of effective solutions for real-world plastic waste characterized by complex structures, diverse types, and vastly differing properties.
Methodology:
The mixed plastic samples were first analyzed by solid-state NMR technique (two-dimensional 1H–13C frequency-switched Lee–Goldburg heteronuclear correlation) to make a reliable identification of the functional groups in the intermingled matrix. Then, to design suitable transformation routes for desired products, catalytic reactions including photo-oxidation, amination, dehydrogenation coupling and hydrocracking were arrayed with solvent-based pre-processes such as selective dissolution and solvolysis reactions interspersed. To cope with the unknown real-world waste, strategically integration of solid-state NMR with complementary techniques such as solution-state NMR, elemental analysis, vibrational spectroscopy, photoelectron spectroscopy and so on was employed.
Key findings:
1. This study innovatively proposed a product-oriented orthogonal transformation strategy, which is based on accurate identification of the characteristic functional groups, utilized the differences in the physical and chemical properties of different plastic components, and is designed in a targeted manner to convert different types of plastics into valuable chemicals in sequence under mild and low-energy conditions.
2. This strategy successfully achieved the directional preparation of mixed plastics into a variety of valuable products. Started with 20g of real-life plastic mixtures composed of polystyrene, polylactic acid, polyurethane, polycarbonate, polyvinyl chloride, polyethylene terephthalate, polyethylene and polypropylene commodities, a group of useful chemicals were obtained, including 1.3 g of benzoic acid
