UiO-type MOFs catalyzed ring-opening copolymerization of epoxides and cyclic anhydrides

Abstract

Ring-opening copolymerization (ROCOP) of epoxide with cyclic anhydride plays critical role in the preparation of polyesters. Herein, the UiO-type MOFs including UiO-66, UiO-66-NH2, UiO-66-NO2, UiO-66-Br and UiO-67 with octahedral morphology were synthesized by different ligands and used as heterogeneous catalysts for ROCOP of epoxide with cyclic anhydride. It was shown that the UiO-67 with ultra-high specific surface area and large pore size endows it with abundant of catalytic active sites and the highest catalytic activity, which makes UiO-67 present seven times higher turnover frequency (192.6 h−1) than that of UiO-66 (23.6 h−1) under the same conditions. Besides, the strong electron-absorbing group enhances the catalytic activity of UiO-type MOFs. The cycling test proves that the UiO-67 has good recoverability and there was no significant loss of catalytic activity after been reused for three times. The kinetic study showed that the ROCOP of epoxide with cyclic anhydride catalyzed by UiO-67 was a first-order kinetic reaction, and its apparent activation energy (Ea) was about 71.75 kJ∙mol−1 calculated by the Arrhenius equation, which was 27.5% lower than that of UiO-66 (98.94 kJ∙mol−1).