Amine-Functionalized Tannic Acid-Derived Hierarchical Porous Carbons for CO ₂ and Antibiotic Removal: Mechanistic and Thermodynamic Insights

Hierarchical porous carbons (HPCs) are emerging as multifunctional materials capable of addressing diverse energy and environmental research due to their tunable pore structure and surface nature. Herein, we report a scalable synthesis of in situ nitrogen- and oxygen-co-doped HPCs using amine-functionalized tannic acid. By adjusting KOH dosage and activation temperature, the resulting HPCs exhibited high surface areas (up to 3411 m² g⁻¹) with well-tailored micro/mesoporous architectures. These structural characteristics enabled the same material platform to be assessed for two environmentally significant yet mechanistically distinct adsorptions of gas-phase CO₂ capture and aqueous-phase antibiotic removal. HPC-1-800 exhibited high CO₂ uptake (7.48 mmol g⁻¹ at 273 K and 1 bar), facilitated by ultramicropore filling and the existence of CO₂-philic N/O-functionalities. In contrast, HPC-3-800 showed outstanding adsorption capacities for sulfamethoxazole (629.0 mg g⁻¹) and ciprofloxacin (549.8 mg g⁻¹) at 298 K, primarily driven by abundant mesoporosity and diverse surface functional groups that promote multiple adsorption interactions. These materials also retained high adsorption performance in synthetic urine and ionic solutions, confirming their robustness under complex conditions. Both adsorption processes were mechanistically elucidated using various analytical techniques, along with kinetic and thermodynamic results. Overall, a unified material design enables HPCs to address both gas-phase carbon capture and aqueous-phase pharmaceutical removal.