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Full circle: ZnII-complexes bearing half-salan ligands facilitate the mild and selective degradation of various commercial polyesters and polycarbonates into value-added products (green solvents and chemical building blocks). We report the first example of discrete metal-mediated poly (bisphenol A carbonate) methanolysis being appreciably active at room temperature, whilst the production of several renewable poly (ester-amides)s demonstrates a completely circular PET waste upcycling approach. ZnII-complexes bearing half-salan ligands were exploited in the mild and selective chemical upcycling of various commercial polyesters and polycarbonates. Remarkably, we report the first example of discrete metal-mediated poly (bisphenol A carbonate) (BPA-PC) methanolysis being appreciably active at room temperature. Indeed, Zn (2)2 and Zn (2)Et achieved complete BPA-PC consumption within 12–18 min in 2-Me-THF, noting high bisphenol A (BPA) yields (SBPA = 85–91%) within 2–4 h. Further kinetic analysis found such catalysts to possess kapp values of 0.28 ± 0.040 and 0.47 ± 0.049 min−1, respectively, at 4 wt%, the highest reported to date. A completely circular upcycling approach to plastic waste was demonstrated through the production of several renewable poly (ester-amide)s (PEAs), based on a terephthalamide monomer derived from bottle-grade poly (ethylene terephthalate) (PET), which exhibited excellent thermal properties. [ABSTRACT FROM AUTHOR]