A Solvent-Free Approach for the Mechanochemical Upcycling of Bio- and Fossil-Based Polyesters Into Value-Added Chemicals and Bio-Based Plasticizers.

Plastic waste poses a major environmental challenge, yet it also represents a valuable feedstock to produce high-value chemicals. In this work, we report an ecofriendly and efficient mechanochemical strategy for upcycling of bio- and fossil-based polyesters under mild conditions into synthetically useful building blocks. Bio-based polyethylene furanoate (PEF), polybutylene furanoate (PBF), and polylactic acid (PLA), as well as fossil-derived polyethylene terephthalate (PET), were successfully transformed into their corresponding transesterification and amidation products in excellent yields using sodium methoxide as a catalyst. These reactions generate the corresponding diol, methanol, and sodium chloride as byproducts, which can be recovered and reused. Furthermore, using the same protocol, PEF was converted into bio-based plasticizers, including diethylhexyl furanate (DEHF) and diisoamyl furanoate (DIAF) in excellent yields. Importantly, the method is not limited to pure polymers but is also effective for commercially available PET- and PLA-based packaging materials. The products were isolated by simple aqueous workup and characterized using NMR, IR, HRMS, and XRD techniques. Overall, this mechanochemical route offers a sustainable, cost-effective, and versatile approach for polyester waste valorization, contributing significantly to a circular plastic economy.