Zinc {ONO} complexes for the chemical recycling of PET and PLA

Nine {ONO} ligands were prepared and treated with ZnEt2 to form a range of complexes. The resulting complexes were characterised in solution through H-1 and C-13{H-1} NMR spectroscopy, and in the solid state through single-crystal XRD and elemental analysis. Moderate reactivity towards lactide polymerisation was demonstrated, with hydroxyl complexes reaching high conversion in 1-2 minutes at 300: 1: 1. All complexes successfully degraded PLA to methyl lactate and the effect of reaction time, temperature and catalyst loading was explored. Zn(4)(2) successfully produced ethyl and n-butyl lactate and was shown to work in ambient conditions, albeit with reduced yield and selectivity. The production of BHET from waste PET was demonstrated with a selection of the most active catalysts. Zn(4)(2) was shown to be capable of sequential PLA/PET degradation and to be tolerant of HDPE/PVC contaminants.