Synergistic enhancement of CO2 capture by co-modified amine-functionalized adsorbents derived from fly ash

The extensive utilization of fossil fuels has accelerated greenhouse gas emissions, triggering climate issues that have become a global concern. The integration of waste valorization with CO 2 capture agent development is recognized as a green, cost-effective, and efficient approach to achieving carbon neutrality and environmental protection. In this study, porous SiO 2 supports (specific surface area 809.35 m 2 /g) are fabricated from coal-fired power plant waste (fly ash) to synthesize a series of co-modified amine-functionalized adsorbents for CO 2 capture. Through a strategic combination of KH550 (Aminopropyltriethoxysilane) hydrolytic grafting and PEHA (Pentaethylenehexaamine) wet impregnation, a polyamine network is constructed, endowing the co-modified adsorbent CS-4K 50PEHA with superior CO 2 uptake (4.933 mmol/g, 70℃) and exceptional thermal stability. Thermogravimetric-infrared analysis and DFT calculations confirmed the chemical bonding of KH550 to the support, with the co-modified adsorbent exhibiting enhanced thermal stability (thermal decomposition temperature 320℃) compared to singly-modified counterparts. Furthermore, the structure-activity relationship between silane coupling agents and the support during hydrolysis is systematically investigated. The synergistic effect of polyamine active sites on the CO 2 adsorption mechanism is elucidated through in situ DRIFTS and DFT simulations. This work provides molecular-level insights into different amine modification strategies for solid waste-based supports, highlighting the significance of cooperative adsorption mechanisms at the intersection of waste valorization and carbon capture technologies. • Mesoporous SiO 2 with a high surface area was successfully synthesized from fly ash. • Multi-amine functional sites were constructed through KH550 grafting and PEHA impregnation. • Covalent grafting of KH550 significantly enhanced the thermal stability. • Dual-modified adsorbent exhibited a CO 2 uptake of 4.933 mmol/g along with high stability. • Synergistic chemisorption pathways between primary amine and polyamine sites were revealed.