Non-cationic hyper-crosslinked ionic polymers with hierarchically ordered porous structures: facile synthesis and applications for highly efficient CO2 capture and conversion

Abstract

Hyper-crosslinked porous ionic polymers (HCPIPs) have garnered significant attention due to their unique ionic properties and high specific surface areas. However, the limited variety of monomers, low ionic density, and difficulty in functionalization restrict their development. Herein, a series of functionalized non-cationic HCPIPs with high ionic density are designed and directly synthesized via an innovative and straightforward approach – anion (and cation) hyper-crosslinking of tetraphenylborate-based ionic liquids (ILs). These HCPIPs offer controllable hydroxyl group content (0–2.40 mmol g⁻¹), high IL content (1.20–1.78 mmol g⁻¹), and large specific surface area (636–729 m² g⁻¹) with hierarchically ordered porous structures. These HCPIPs demonstrate exceptional CO₂ adsorption capacities and CO₂/N₂ adsorption selectivities, reaching up to 2.68–3.01 mmol g⁻¹ and 166–237, respectively, at 273 K and 1 bar. Furthermore, these ionic porous materials serve as highly efficient heterogeneous catalysts for CO₂ cycloaddition to epoxides under mild conditions (1 bar CO₂, 60–80 °C, 12–24 h). Notably, the CO₂ adsorption performances and catalytic activities of these HCPIPs are regulated by the hydroxyl groups within their structures, with enhancements observed as the number of hydroxyl groups increases. This work presents a facile and widely applicable method for constructing high-performance and task-specific HCPIPs.