Electromagnetically Heating and Oscillating Liquid Metal for Catalyzing Polyester Depolymerization

Depolymerization and recycling of polyesters have shown great significance to economy, ecology, carbon neutrality and human health. Efficient catalysts for thermolysis depolymerization have long been pursued to achieve rapid depolymerization, high selectivity, and low energy consumption. In this study, it is found that liquid metal (LM) can serve as the efficient self-heater, mechanic disturber and catalyst for thermolysis depolymerization of polyesters under alternating electromagnetic fields. When dissolving different metals (e.g., Sn, Zn, Al, and Mg) into gallium, LMs may provide dynamic interactions between the catalyst and reactants, spontaneous metal enriching, and oxidation within the LM surface layer. Without any conventional heaters and mechanic shakers, polycaprolactone is catalytically depolymerized into ɛ-caprolactone at the rate of ≈700 mg h^-1 mL^-1 with the selectivity of 95.5%. The high surface tension and high mobility of LM also enable continuous depolymerization at an appropriate feeding speed of polyesters (including polyethylene terephthalate, polyhydroxybutyrate and polylactic acid). Thus, this study may offer an unprecedented "all-in-one" platform of liquid metal for continuous thermolysis depolymerization of polyesters, while without any requirement of external heater, mixer, and catalysts.