Enhancing catalytic activity via metal tuning of zeolitic imidazole frameworks for ring opening polymerization of L-lactide

A catalyst series of zeolitic imidazole frameworks (ZIFs) with a sodalite (SOD) structure was explored as an effective heterogeneous catalyst for L-lactide polymerization into biodegradable polylactides (PLAs). The catalyst series of ZIF-8, ZIF-67, and bimetallic ZnCo-ZIF was synthesized under the green method (room temperature synthesis), which contained a variance in the metal species/contents. The chemical and physical properties of catalysts were characterized by several techniques to illustrate the relation between catalyst properties and catalytic performance. The results indicated that the metals in the ZIF structure revealed an influencing role in catalytic activities, kinetic rates, and properties of polymer products under bulk ring-opening polymerization of L-lactide. Moreover, the best performing ZIF showed potential as a heterogeneous catalyst since it could be reused at least four times without significant loss of catalytic activity.