Ti(OH)4-assisted amine-modified silica aerogels for enhancing CO2 adsorption capacity and amine efficiency

Abstract

Amine-modified silica aerogels are promising CO2 sorbents owing to their high surface area, tunable pore structure, and strong chemisorption interactions between CO2 and amine groups. However, their amine efficiency and adsorption capacity remain limited for practical applications. In this study, Ti(OH)4 was introduced as an additive to enhance both the structural and functional performance of amine-grafted silica aerogels. The incorporation of Ti(OH)4 modified the pore structure, improved the dispersion of amine groups within the silica network, and increased the number of available hydroxyl groups. As a result, the Ti(OH)4-containing samples exhibited improved CO2 capture performance and higher amine efficiency under both dry and humid conditions. Detailed analyses further reveal that the additive promoted the formation of bicarbonate intermediates in humid environments, leading to a significant enhancement in adsorption performance. This was supported by TPD-MS results, which showed an increased ratio of desorbed H2O to CO2, indicating that Ti(OH)4 actively participated in the cooperative reaction between CO2, H2O, and amine species. The additive-containing sample achieved amine efficiencies of up to 0.475 mol-CO2/mol-N under dry conditions and 0.905 mol-CO2/mol-N under humid conditions, which is substantially higher than that of the additive-free sample. These findings demonstrate that Ti (OH)4 serves as an effective multifunctional additive that enhances amine dispersion and improves CO2-amine interactions, providing a suitable strategy for developing high-performing amine-based CO2 adsorbents for practical applications.