Facile functionalization iron in zeolitic imidazole framework-67 under solvent-free conditions for enhancing CO<inf>2</inf> fixation reaction

Abstract

The heterometal functionalization on zeolitic-imidazole frameworks (ZIFs) is a strategy to modify properties over the homometal ZIFs. A green strategy for simultaneously functionalized iron atoms during the crystal formation of ZIF-67 (Fe@ZIF-67) through the solid-solid thermal (SST) method is newly developed. The single-step process and absent solvent conditions are beneficial advantages of this SST method over the early reported synthetic methods. The results show that the iron is well-dispersed and homogeneously coordinated in the structure of Fe@ZIF-67. Moreover, the optimal iron-functionalized ZIF-67 (20Fe@ZIF-67) significantly enhances the catalytic performance of CO2 cycloaddition epoxide by 2.3 times compared to pristine ZIF-67 under mild reaction conditions. The DFT calculation reveals that the iron atom induces the unsaturated sites or defect structure on the Fe@ZIF-67 catalyst, providing more reactive sites for the catalytic activity of the reaction.