Alkyl-chain-tuned hierarchically porous ionic polymers with ultrahigh surface area for CO2 adsorption and conversion

• Alkyl-tailored PHAIPs enable concurrent CO 2 capture/conversion via dual-active sites. • Alkyl-modulated multicomponent strategy constructs hierarchical porosity with ultra-high S BET . • Synergistic framework kinetics revealed by DFT calculations. • Integrated experimental, isotherm, and thermodynamics analyze CO 2 adsorption. Porous ionic polymers (PIPs) featuring high specific surface area ( S BET ) and abundance of ionic active sites have emerged as advanced materials for synergistic CO 2 capture and conversion. In this study, a novel class of hydroamino-functionalized ionic polymers, designed as PHAIPs, was constructed through a one-pot three-component strategy integrating Friedel-Crafts alkylation, quaternization, and nucleophilic epoxide ring-opening reactions. The synthesis employed α , α’ -dibromo-p-xylene, N , N -dimethylethylene diamine and glycidyl-dimethyl-alkyl-ammonium bromide as modular building blocks, facilitating precise control over textural properties. Systematic structural optimization through alkyl chain length variation and reactant stoichiometric adjustments generated ionic polymers with tunable S BET up to 1731 m 2 ·g −1 and hierarchical pore architecture. The optimized PHAIP-C 16 exhibited a moderate CO 2 adsorption capacity of 2.45 mmol·g −1 and a CO 2 /N 2 selectivity factor of 71 at 1 bar, governed by a synergistic Langmuir and Freundlich adsorption mechanism with thermodynamically spontaneous and exothermic characteristics. Notably, the PHAIP-C 16-4/3/1.5 demonstrated particularly effectiveness in CO 2 cycloaddition reactions, achieving an excellent conversion yield of 95.5%. Mechanistic investigations revealed a dual-activation pathway, with bromide anion (Br − ) nucleophilically activated epoxides, while hydroamino groups function as hydrogen-bond donors to stabilize transition states and intermediates. Density functional theory (DFT) calculations corroborated this synergistic mechanism, confirming the critical role of ionic/hydrogen-bonding networks in lowering activation barriers. This work establishes a rational design strategy for multifunctional ionic polymers in carbon capture and utilization.