Exploration of structured solid amine adsorbents for CO₂ capture: PEI-loaded composite foam material

Solid amine adsorbents are widely employed for CO₂ capture due to their high selectivity and renewability. However, most existing adsorbents are in powdered form, and current shaping methods often suffer from poor universality, complex synthesis procedures, low mechanical strength, or pore structure degradation-factors that significantly hinder industrial application. To address these challenges, a scalable and cost-effective strategy is proposed for fabricating structured solid amine adsorbents by combining porous materials (e.g. biochar), industrial waste-based sulfur-aluminum cementitious binders, and H₂O₂-assisted chemical foaming. This process integrates micro-mesopores derived from the porous materials with macropores generated through foaming and hydration, resulting in a 3D interconnected hierarchical pore structure. The structured adsorbent exhibits excellent compressive strength (∼77.33 N), competitive CO₂ adsorption capacity (60.04 mg/g at 90°C), high amine utilization (68.52%), and good reusability (only a 7.59% reduction after five cycles). Kinetic analysis reveals that 76.38% of the total CO₂ adsorption capacity occurs within the first 2 min, indicating a rapid initial adsorption rate despite structural shaping. Moreover, the proposed method is successfully extended to other carriers such as synthetic resin and nano-fumed silica, demonstrating strong material adaptability. In addition to adsorption capacity, this study emphasizes amine utilization as a key performance metric and introduces a novel evaluation chart for the simultaneous assessment of both parameters. Overall, this work addresses pressing challenges in shaping, mechanical strength, and cost, and offers an effective, scalable pathway for the practical deployment of solid amine adsorbents in CO₂ capture technologies.