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

• Ti(OH)₄ additive improves amine dispersion and pore structure of silica aerogel • Ti(OH)₄ enhances CO₂ capture capacity under dry and humid sorption conditions • Ti(OH)₄ promotes bicarbonate formation and amine efficiency under humid CO 2 sorption • Synthesized samples show potential for practical and direct air capture applications Amine-modified silica aerogels are promising CO 2 sorbents owing to their high surface area, tunable pore structure, and strong chemisorption interactions between CO 2 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 CO 2 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 H 2 O to CO 2 , indicating that Ti(OH) 4 actively participated in the cooperative reaction between CO 2 , H 2 O, and amine species. The additive-containing sample achieved amine efficiencies of up to 0.475 mol-CO 2 /mol-N under dry conditions and 0.905 mol-CO 2 /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 CO 2 -amine interactions, providing a suitable strategy for developing high-performing amine-based CO 2 adsorbents for practical applications.