Polyethylene terephthalate (PET), as an important thermoplastic polyester, has an annual global production exceeding 70 million tons and is widely used in everyday food packaging, textiles, and other fields. However, behind this massive production volume, approximately 80% of waste PET is indiscriminately discarded or landfilled, causing severe environmental pollution and leading to the waste of substantial carbon resources. How to achieve the recycling of waste PET has become a critical challenge requiring breakthroughs for global sustainable development.
Among existing recycling technologies, photoreforming technology has garnered significant attention due to its green and mild characteristics. This technique utilizes clean, non-polluting solar energy as the driving force, generating active redox species in situ under ambient temperature and pressure to facilitate the conversion and value-added upgrading of waste plastics. However, the products of current photoreforming processes are mostly limited to simple oxygen-containing compounds such as formic acid and glycolic acid.
Recently, a research team from the Center for Photochemical Conversion and Synthesis at an institute in China proposed using waste PET and ammonia as carbon and nitrogen sources, respectively, to produce formamide via a photocatalytic C-N coupling reaction. To this end, the researchers designed a Pt1Au/TiO2 photocatalyst. In this catalyst, single-atom Pt sites selectively capture photogenerated electrons, while Au nanoparticles capture photogenerated holes, significantly enhancing the separation and transfer efficiency of photogenerated electron-hole pairs, thereby boosting photocatalytic activity. The formamide production rate reached approximately 7.1 mmol gcat⁻¹ h⁻¹. Experiments such as in-situ infrared spectroscopy and electron paramagnetic resonance revealed a radical-mediated reaction pathway: photogenerated holes simultaneously oxidize ethylene glycol and ammonia, generating aldehyde intermediates and amino radicals (·NH₂), which undergo C-N coupling to ultimately form formamide. This work not only pioneers a new pathway for the high-value conversion of waste plastics, enriching the spectrum of PET upgrade products, but also provides a greener, more economical, and promising synthetic strategy for the production of important nitrogen-containing compounds such as pharmaceuticals and pesticides.
The related research findings were published in Angewandte Chemie International Edition under the title “Photocatalytic Formamide Synthesis from Plastic Waste and Ammonia via C-N Bond Construction Under Mild Conditions”. The research received funding from projects supported by the National Natural Science Foundation of China, the Joint Laboratory Fund for Novel Materials between the Chinese Academy of Sciences and The University of Hong Kong, among other sources.
Post time: Sep-26-2025