Heat Treatment of Fe-doped Zr-MOF Catalysts for Dual Lewis Acid Sites Promoted CO₂ Cycloaddition

The activation and transformation of CO2 into high value-added chemicals are very promising for meeting the carbon neutrality. Lewis acids are attractive in CO2 catalytic activation due to the fact that the O atom of CO2 can be attacked by the electrophilic centers. Here, a series of single-atom Fe-doped Zr-MOF nanocatalysts, denoted as Fe-ZrMOF-T, are prepared. The coordination environment for Fe single atoms can be modulated by heat treatment, which shows influence on the expression of Lewis acidity and affects the catalytic ability toward the CO2 cycloaddition. It was found that Fe-ZrMOF-5 obtained by heat treatment at 500 °C possesses the highest activity. Results show the synergistic effect between the dual Lewis acid sites of Fe3+ and Zr4+ on this Lewis acid catalysis, in which Fe3+ is prone to activate epoxides while Zr4+ prefers to react with CO2. The corresponding reaction mechanism was proposed based on these findings.