Fabrication of Small-Sized ZIF-8 Confined in the Mesoporous SBA-15 with Synergistic Enhancement for CO2 Fixation with Epoxides

The novel hybrid materials of ZIF-8 with mesoporous SBA-15 were fabricated through a facile layer-by-layer assembly strategy, and their catalytic performances for cycloaddition reaction between CO 2 and epoxide were also preliminarily explored. The structure features and physicochemical properties of the obtained ZIF-8/SBA-15 by means of various characterizations demonstrated that SBA-15, acting as a structure-directing agent, could not only induce the nucleation of ZIF-8 directionally through the coordination interaction between Zn 2+ and silanol groups, but also control the growth of the nanocrystals via the confined space of mesoporous channels. These results easily led to a sharp decrease in the crystal sizes of ZIF-8, accompanied with extensive exposure of the active sites. Particularly, the stability of ZIF-8 distributed in the mesopores of SBA-15 was improved significantly, despite their small size and low coordination. Therefore, the activity of the 5th recycled hybrid catalysts was almost twice that of ZIF-8. This strategy not only facilitates the preparation of a high-efficiency catalyst for cycloaddition reaction, but also opens up a path for synthesis of other metal–organic frameworks (MOFs)/silica materials, which is greatly anticipated for a wide variety of applications. Graphical Abstract