Role of Aromatic Topology in Hyper-Crosslinked Polymers on CO2 Adsorption and CO2/N2 Selectivity

Abstract

Despite extensive studies of hyper-crosslinked polymers (HCPs) for carbon dioxide adsorption and separation, the fundamental role of aromatic precursor topology in governing localized gas confinement and molecular recognition has remained poorly understood. Herein, we demonstrate that the geometric topology of aromatic precursors, spanning isolated aromatic rings, rigid fused polycyclic frameworks, and rotationally flexible biaryl linkages, directly controls framework packing and micropore generation. Systematic variation of precursor topology reveals distinct relationships between porosity, adsorption affinity, and molecular selectivity. Comprehensive structural, thermodynamic, and adsorption analyses, including Henry’s law constants (K_H), isotherm model fitting, and isosteric heats of adsorption (Q_st), reveal that topology-controlled confinement may promote cooperative multi-body interactions. Benzene-derived HCP, with the most accessible ultra micropores, delivers the highest CO₂ uptake (74.0 cm³ g^–1 at 273 K and 1 bar) and K_H (109 mmol g^–1 bar^–1). Anthracene-derived HCP, with its rigid fused-ring geometry, instead achieves the highest CO₂/N₂ selectivity (557 at 273 K and 0.01 bar) and Q_st (32.0 kJ mol^–1), suggesting a possible contribution from cooperative multi-body interactions between CO₂ and the confined aromatic framework. This enhanced energetic interaction is accompanied by suppressed N₂ adsorption, rather than by increased CO₂ capacity. Overall, these results demonstrate that CO₂ uptake and CO₂/N₂ molecular discrimination arise from distinct aspects of framework architecture, highlighting aromatic precursor topology as a key structural parameter for tuning gas adsorption and separation in HCPs.