Amine post-functionalized POSS-based porous polymers exhibiting simultaneously enhanced porosity and carbon dioxide adsorption properties

Abstract

A novel hybrid porous polymer (HPP-1) is synthesized using octavinylsilsequioxane and 2,7-dibromo-9-fluorenone as monomers via Heck reaction. Subsequently, HPP-1 is post-functionalized by the conversion of deliberately introduced free ketone moieties into amine functionalities. Compared with HPP-1, the resulting material, HPP-1-amine, showed enhanced CO₂ uptake from 0.63 mmol g⁻¹ (HPP-1) to 1.01 mmol g⁻¹ (HPP-1-EDA, EDA = ethylenediamine) and 0.72 mmol g⁻¹ (HPP-1-HDA, HDA = hexamethylenediamine) at 298 K and 1 bar. Furthermore, the porosity of HPP-1-amine is not compromised, but enhanced with the BET specific surface area increasing from 529 m² g⁻¹ (HPP-1) to 651 m² g⁻¹ (HPP-1-EDA) and 615 m² g⁻¹ (HPP-1-HDA). Compared with HPP-1, the selectivity of CO₂ over N₂ of HPP-1-EDA increases nearly twice while that of HPP-1-HDA slightly decreases, indicating their potential applications in CO₂ storage and capture. Although the enhanced extent of CO₂/N₂ selectivity is not as high as other analogues, we provide a new possibility for post-synthetic amine functionalization of porous polymers for simultaneously enhancing porosity and CO₂ adsorption properties. The retained porosity won't limit their applications in other areas, such as heavy metal ion adsorption, ion channels and catalysis, etc.