Designed synergetic bifunctional catalyst based on diverse nucleophilic-functionalized sites for high-efficient CO2 cycloaddition under co-catalyst and solvent-free conditions

Nucleophilic substitutes provide a new platform to design and synthesize novel bifunctional heterogeneous catalysts for carbon dioxide cycloaddition reaction with epoxides. Herein, in this work, UMCM-15 was fabricated and modified with various nucleophilic ligands containing bromine, amine and hydroxyl functional groups. The resultant prepared compounds were utilized as bifunctional synergetic catalysts for the chemical fixation of carbon dioxide. The catalysts can efficiently catalyze epoxides and carbon dioxide under relatively mild conditions in the absence of co-catalyst and solvent. The contemporaneous presence of Lewis acid and basic centers in the framework resulted in high catalytic activity and turnover number (TON) value for the production of cyclic carbonates compared to other reported compounds indicating superiority of the synthesized catalysts. Among diverse applied bifunctional catalysts, bromine-functionalized frameworks exhibited the highest catalytic performance owing to the presence of multiple electron pairs and the great tendency to donate electron pairs.