POSS and imidazolium-constructed ionic porous hypercrosslinked polymers with multiple active sites for synergistic catalytic CO2 transformation

Abstract

In this work, we reported a facile one-pot approach to construct polyhedral oligomeric silsesquioxane (POSS) and imidazolium-based ionic porous hypercrosslinked polymers (denoted as iPHCPs) with multiple active sites towards efficient catalytic conversion of carbon dioxide (CO₂) to high value-added cyclic carbonates. The targeted iPHCPs were synthesized from a rigid molecular building block octavinylsilsesquioxane (VPOSS) and a newly-designed phenyl-based imidazolium ionic crosslinker through the AlCl₃-catalyzed Friedel–Crafts reaction. The desired multiple active sites come from the mixed anions including free Cl⁻ and Br⁻ anions, and in situ formed Lewis acidic metal–halogen complex anions [AlCl₃Br]⁻ within imidazolium moieties and POSS-derived Si–OH groups during the synthetic process. The typical polymer iPHCP-12 possesses a hierarchical micro-/mesoporous structure with a high surface area up to 537 m² g⁻¹ and shows a fluffy nano-morphology. By virtue of the co-existence of free nucleophilic Cl⁻ and Br⁻ anions, the metal complex anion [AlCl₃Br]⁻ with both electrophilic and nucleophilic characters and electrophilic hydrogen bond donor (HBD) Si–OH groups, iPHCP-12 is regarded as an efficient recyclable heterogeneous catalyst for synergistic catalytic conversion of CO₂ with various epoxides into cyclic carbonates under mild conditions. The present work provides a succinct one-pot strategy to construct task-specific ionic porous hypercrosslinked polymers from easily available modules for the targeted catalytic applications.