Mg(OTf)₂ as an Excellent Catalyst for the Reductive Depolymerization and Methanolysis of Polyesters and Polycarbonates

Abstract The use of alkaline earth‐abundant metal catalysts as alternatives to transition metal catalysts in the depolymerization of plastic waste is a very important research area. In this work, the first method is described for the conversion of polyesters into value‐added compounds catalyzed by a magnesium catalyst. It is demonstrated that the commercially available, inexpensive and air‐stable, alkaline earth magnesium catalyst Mg(OTf)₂ efficiently promotes the reductive depolymerization of several polyesters using pinacolborane (HBpin) as the reducing agent with good to excellent yields. This catalyst also remains very active in at least 12 consecutive polycaprolactone (PCL) reductive depolymerization reactions with yields between 89% and 81%. This magnesium catalyst is also efficient in the reductive depolymerization of the polycarbonate poly(bisphenol A carbonate) (PC.BPA). Furthermore, it is found that Mg(OTf)₂ also successfully catalyzes the methanolysis of polyesters and polycarbonates at moderate temperature with excellent yields.