Functional upcycling waste polyethylene terephthalate plastics for high near-infrared reflective pigment via controlled molecular reconstruction

A significant upcycling strategy for waste PET via mild molecular reconstruction. • Record-breaking NIR solar reflectance of 96.95%. • Surface temperature reduction of 12.2 °C compared to commercial pigments. Post-consumer polyethylene terephthalate (PET) plastics constitute the largest portion of persistent polyester solid waste, while conventional recycling is limited to low-value mechanical regeneration or closed-loop monomer repolymerization with unsatisfactory economic value. Additionally, commercial organic pigments heavily rely on non-renewable petroleum-based aromatic feedstocks accompanied with potential toxicity issues. In this work, we report a significant upcycling strategy for waste PET bottles toward functionally purple NIR-reflective pigments via mild modular molecular reconstruction. The resulting pigment exhibited a vivid purple hue (L∗ = 50.11, a∗ = 39.66, b∗ = -15.68) and pronounced photoluminescence, emitting brilliant yellow light centered near 600 nm under UV excitation. Notably, the pigment achieved a significantly high NIR solar reflectance of 96.95%. Organic coatings formulated with this pigment demonstrated a surface temperature reduction of 12.2 °C relative to coatings employing a commercial purple analogue, together with superior hiding power. Furthermore, these coatings displayed robust stability retaining a maximum NIR reflectance exceeding 80% after aging. Mechanistic analysis revealed that the exceptional NIR reflectance originated predominantly from multiple scattering, intensified light scattering, and synergistic optical interactions. This work breaks the value ceiling of traditional PET recycling, establishes a sustainable non-petroleum feedstock paradigm for organic pigment industry, and provides a universal avenue for high-value upcycling of bulk polyester plastic waste toward advanced functional materials. Download: Download high-res image (288KB) Download: Download full-size image