Mechanochemical construction of mesoporous silicon-supported organocatalysts with alkylol-amine cooperative sites for CO2 fixation into cyclic carbonates under halogen-free conditions

In this work, we demonstrated a mechanochemical method to quickly fabricate mesoporous SiO 2 -supported organocatalysts with alkylol-amine cooperative sites. The detailed characterizations of solid-state NMR, FTIR, XPS, TGA, as well as electron microscope confirmed that the organocatalysts were successfully grafted on the surface of SiO 2 by mechanically ball-milling without any solvent. These SiO 2 -supported organocatalysts exhibit medium to remarkable activity for the cycloaddition of CO 2 and epoxides under halogen- and solvent-free conditions, and the activity of the catalysts can be also adjusted by controlling the pore size of the support SiO 2 and the structure of organocatalysts. Further mechanistic studies suggest that the good activity originates from the synergistic effect between the alkylol and amine sites. Furthermore, SiO 2 -supported organocatalysts can be easily recovered and recycled. This work not only provides an efficient method for the agile construction of multifunctional organic-inorganic hybrid materials, but also provides an alternative halogen-free catalyst for CO 2 conversion.