Directionally induced hydrogen bonding interactions of heteroatom-incorporated amine adsorbents for promoting steady CO2 capture†

Abstract

Insufficient cyclic stability due to urea formation at high temperatures has been an obstacle for solid amine adsorbents in expanding CO₂ capture applications. Herein, a simple and scalable synthesis of PEI-impregnated silica with heteroatom incorporation (such as metal) is reported, which increases cyclic stability by 46.5% and improves the heat resistance by 24.4%, while maintaining an excellent adsorption capacity of over 170 mg g⁻¹ across a wide-temperature range. The impact of hydroxyl groups and hydrogen bonds on the CO₂-induced degradation of heteroatom-incorporated silica with amine modification is also explored in detail. By combining CO₂ adsorption measurements, cyclic experiments, FTIR spectroscopy, and in situ DRIFTS analysis in conjunction with quantum chemical calculations, a comprehensive picture of urea formation is obtained. We have innovatively demonstrated that the presence of hydroxyl groups can have a dual effect through hydrogen bonds on urea formation. The directional induction of hydrogen bonds by metal incorporation significantly improves the cyclic stability. The proposed mechanism can be extended to similar elements with lower electronegativity than Si. This study paves the way for investigations into carbon capture chemistry that can guide the synthesis of novel solid amine adsorbents for anti-urea formation.