Mechanochemically functionalized waste plastics for NO₂ sensing

Low-entropy non-depolymerizing upcycling of waste plastics into value-added products is promising, as it can avoid energy-intensive depolymerization process. Here, we report a mechanochemical approach for the direct functionalization of plastics with polyoxometalate (POM) molecules. The resulting POM-plastic composites retain integrated plastic chains and exhibit strong potential for NO₂ sensing. Among the composites, phosphotungstic acid/polyethylene terephthalate (PW₁₂-PET) achieves a low limit of detection (10.52 ppb) and fast response/recovery times (19.2 s/13.5 s at 5.0 ppm), and shows practical applicability after device assembly. Moreover, it exhibits high selectivity against ten interfering gases. Mechanistic studies reveal that PET transfers multiple charges to PW₁₂. It not only activates new bridge-oxygen sites on PW₁₂ but also maintains a moderate adsorption strength, enabling rapid NO₂ response. This work represents a promising example of direct non-depolymerizing upcycling of waste plastics into value-added functional materials.