Development of Amino-Functionalized Silica by Co-condensation and Alkylation for Direct Air Capture.

CO chemisorption using amine-based sorbents is one of the most effective techniques for carbon capture and storage. Solid CO sorbents with amines immobilized on their surface have been attracting attention due to the easy collection of sorbents and reusability. In this study, we developed a solid CO adsorbent by co-condensation of a silanizing reagent having a chloroalkyl group and tetraethyl ethoxysilane, followed by alkylation of the chloroalkyl group with diamine. The fabricated amine-immobilized silica with a high density of amino groups on its surface achieved the chemical adsorption of 400 ppm of CO with 4.3 wt % loading, CO release upon heating at 80 °C, and reusability for adsorption and desorption cycles with high amine utilization efficiency (0.20 mol /mol). This surface modification method is applicable to various amines bearing more than two amino functional groups, enabling the development of solid CO sorbents for the selective capture of low-concentration CO directly from the air.