An Oxalate‐Bridged Binuclear Iron(III) Ionic Liquid for the Highly Efficient Glycolysis of Polyethylene Terephthalate under Microwave Irradiation

An oxalate-bridged binuclear iron(III) ionic liquid combined with an imidazolium based cation, (dimim)2 [Fe2 Cl4 (μ-ox)], was synthesized and characterized by a wide range of techniques. This halometallate ionic liquid was active in catalyzing the depolymerization of polyethylene terephthalate (PET) by glycolysis, under conventional and microwave-assisted heating conditions. Both methodologies were very selective towards the production of bis(2-hydroxyethyl)terephthalate (BHET). The employment of microwave heating proved beneficial in terms of time and energy saving when compared to the use of thermal heating. Indeed, dielectric spectroscopy studies revealed that the binuclear iron-containing ionic liquid exhibits an excellent heating response under an electromagnetic field. The catalyst provided quantitative conversions to BHET in the glycolysis of post-consumer PET bottles in only 3 h through microwave heating, as compared to 80 % conversion after 24 h under conventional heating.