Hydroxyl-functionalized microporous polymer for enhanced CO₂ uptake and efficient super-capacitor energy storage

In recent years, porous organic polymers (POPs) have received increasing attention and research interest due to their formidable potential applications in gas storage/separation, heterogeneous catalysis, photoelectricity, energy storage and conversion, etc. In this work, we report the design and synthesis of a hydroxyl-functionalized porous organic polymer (PCz-res) by conventional FeCl₃-facilitated oxidative polymerization for gas adsorption and energy storage applications. The precursor Cz-res was designed and synthesized by the imidization of anhydride bearing twisted carbazole units with 4,6-diaminoresorcinol. The prepared PCz-res polymer was completely characterized by the usual analytical techniques. PCz-res exhibited a high specific surface area of 1015 m²/g and reversibly adsorbed 20.53 wt% (273 K) and 14.92. wt% (295 K) CO₂ at 1 bar with a moderate isosteric heat of CO₂ adsorption (22.39 kJ/mol). The favourable properties of PCz-res were attributed to the uniform pore size distribution (0.8 nm), high surface area, rich nitrogen content and presence of polar CO₂-philic hydroxyl groups in the polymeric network. These features make the investigated polymer a plausible emerging material in the field of gas adsorption and separation. Moreover, PCz-res was applied in supercapacitor energy storage and exhibited a specific capacitance as high as 434 F g⁻¹ in 1 M H₂SO₄ at a 2 mV/s scan rate and 367 F g⁻¹ at a current density of 0.5 A g⁻¹. Additionally, PCz-res retained 91% of the initial specific capacitance after 2000 charge/discharge cycles at a current density of 10 A g⁻¹. The structural characteristics of PCz-res lead to a larger accessible surface area and a redox-active structure, resulting in efficient charge energy storage.