Metal-organic frameworks (MOF) are porous materials made up of organic binders and a metal cluster, currently attracting attention as heterogeneous catalysts in various reactions of interest. However, their application in ring-opening polymerization (ROP) reactions of cyclic esters has not been sufficiently explored yet. In this work, study of zirconium-based MOF as a catalyst in ε-caprolactone (ε-CL) ring opening polymerization in the presence of benzyl alcohol is reported. These catalysts were synthesized through solvothermal methods using N,N-dimethylformamide (DMF) as solvent and replaced by methanol. Polymerization reactions were carried out at 150 and 170 °C for time intervals of 1 to 4 hours, under nitrogen atmosphere. The monomer conversion and the average number molecular weight (Mn) were monitored and determined through proton nuclear magnetic resonance spectroscopy (1H NMR). Synthesized MOFs have high thermal stability, showing complete framework degradation at 550 °C, thus behaving as promising catalysts for ɛ-CL ROP. Polymers with number molecular weights within the range 3211 to 6843 Da were obtained. It is important to mention that it was possible to verify the recyclability of these materials, by reusing them in up to five polymerization cycles, obtaining for each of them, high percentages of conversion.
Authors: Mónica Ayala Gómez*, Gerardo González-García, José E. Báez García, Patricia Quintana Owen, Laura Diñeiro García*, Rodrigo Navarro