Scheme 3. CaO-catalyzed Chemical Depolymerisation of the Polyesters Also, the chemical depolymerization of two aromatic (HN_FDCA (10), HM_FDCA ( ) and two aliphatic (HN_DMS (11), HM_DMS (15) polyesters was performed by metal oxide-catalyzed transesterification in ethanol (Scheme 3). Inspired by previous work, CaO, MgO, and MgO-CaO were explored as catalysts and we found that CaO is superior in performance in recycling.