Hierarchical pore and polarity regulation synergistic promoting efficient CO₂ adsorption

To address the two major challenges of low active site utilization and amine loss in traditional amine-functionalized CO₂ adsorbent, this study proposed a synergistic strategy of “hierarchical pore channels-polarity regulation”. Using hierarchical mesoporous silica (HMS) as the support, a dual-functional modification approach combining aminopropyltrimethoxysilane (APTMS) and butyltrimethoxysilane (BTMS) grafting with tetraethylenepentamine (TEPA) impregnation was employed to construct an efficient CO₂ adsorption system with dual active sites. APTMS and BTMS were alternately grafted onto the HMS via siloxane bonds, resulting in a structure with varying polarities. The strong polarity of TEPA interacts simultaneously with the terminal groups of APTMS and BTMS, facilitating the uniform dispersion of TEPA within the material. The optimized HMS-AB-70T adsorbent exhibited a dynamic CO₂ adsorption capacity of 5.34 mmol g⁻¹ at 70 °C, with a reduction of 9.8 % in adsorption capacity after 10 cycles. In a humid environment, its performance was further enhanced to 5.89 mmol g⁻¹. The CO₂ adsorption mechanism was revealed by in situ infrared spectroscopy and kinetic analysis, involving the formation of carbamate and bicarbonate species. By adjusting the hydrophilic-lipophilic balance of the P123 template, a hierarchical mesoporous structure of HMS (∼6 nm and ∼10 nm) was successfully achieved, promoting rapid mass transfer and providing abundant adsorption sites. This strategy offers a novel molecular-level approach for the design of efficient and stable CO₂ adsorbents.