Silanol-Enriched Viologen-Based Ionic Porous Hybrid Polymers for Efficient Catalytic CO2 Fixation into Cyclic Carbonates under Mild Conditions

In this work, we report a new family of viologen-based ionic porous hybrid polymers (V-iPHPs) with task-specific multiple catalytic active sites toward efficient catalytic fixation of carbon dioxide (CO2) to value-added cyclic carbonates. The targeted V-iPHPs were fabricated by the solvothermal Heck reaction between two newly designed viologen ionic linkers and octavinylsilsesquioxane (VPOSS). The obtained V-iPHPs possess tunable surface areas (150-562 m(2) g(-1)) and pore volumes (0.41-1.82 cm(3) g(-1)) along with adjustable ionic sites (0.92-1.47 mmol g(-1)). Especially, a plenty of silanol (Si -OH) groups are in situ formed via breaking polyhedral oligomeric silsesquioxane cages during the synthetic process. The typical catalyst V-iPHP-1 exhibits remarkable metal-free heterogeneous catalytic activities in the CO, fixation with diverse epoxide substrates under very mild conditions. Besides, the heterogeneous catalyst V-iPHP-1 could be easily recovered with good reusability. The excellent catalytic performance could be assigned to the synergistic catalysis of hydrogen bond donors Si-OH groups and Br- anions, abundant mesoporosities, and the hydrophobic reaction microenvironment.