Rapid, Microwave-Assisted Synthesis of Cubic, Three-Dimensional, Highly Porous MOF-205 for Room Temperature CO₂ Fixation via Cyclic Carbonate Synthesis

Abstract

A dual-porous, three-dimensional, metal-organic framework [Zn₄O(2,6-NDC)(BTB)_4/3] (MOF-205, BET = 4200 m²/g) has been synthesized using microwave power as an alternative energy source for the first time, and its catalytic activity has been exploited for CO₂-epoxide coupling reactions to produce five-membered cyclic carbonates under solvent-free conditions. Microwave synthesis was performed at different time intervals to reveal the formation of the crystals. Significant conversion of various epoxides was obtained at room temperature, with excellent selectivity toward the desired five-membered cyclic carbonates. The importance of the dual porosity and the synergistic effect of quaternary ammonium salts on efficiently catalyzed CO₂ conversion were investigated using various experimental and physicochemical characterization techniques, and the results were compared with those of the solvothermally synthesized MOF-205 sample. On the basis of literature and experimental inferences, a rationalized mechanism mediated by the zinc center of MOF-205 for the CO₂-epoxide cycloaddition reaction has been proposed.