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In this study, highly cross-linked and completely imidized polyimide aerogels containing carboxyl groups were successfully synthesized using a mild sol-gel method at room temperature from 3,5-diaminobenzoic (DABA) and biphenyl-3,3′,4,4′-tetracarboxylic (BPDA) and cross-linked with 1,3,5-triaminophenoxybenzene. The densities of the obtained polyimide aerogels are between 0.116 and 0.386 g/cm 3 , the specific surface areas range from 173 to 461 m 2 /g, and the porosities are as high as 97%. The CO 2 adsorption-desorption isotherms are reversible, and the CO 2 uptakes at 25 °C and 1 bar are as high as 21.10 cm 3 /g, which are comparable to those of previously reported microporous organic polymers. The high CO 2 adsorptions are attributed to the abundance of electron-rich heteroatoms in the polyimide networks and to the presence of carboxyl groups, a type of CO 2 -philic group. The facile preparation and high CO 2 adsorptive capacity indicate that polyimide aerogels may be ideal candidates for capturing CO 2 . [ABSTRACT FROM AUTHOR]

The objective of this research was to develop a high-performance CO 2 adsorbent by a simple, cost-effective and environmental-friendly route based on amine hybrid aerogel. A new amine hybrid titania/silsesquioxane composite aerogel (AHTSA) was prepared by a one-pot sol-gel process followed by supercritical drying (SCD). The wet gel was obtained by orderly mixing all the reactants in a container without adding any catalyst. SCD was conducted without contaminant emission. Effects of amine loading and CO 2 concentration on pores structure and CO 2 adsorption performance of AHTSA were investigated. Higher amine loading leads to lower specific surface area and mesopore volume of AHTSA, due to the increase of large pores and diminishment of mesopores when increasing the amine loading. Resulting from the sharp decrease of the surface area, overdosing of the amine precursor negatively affects the surface amine content of AHTSA and thus reduces its CO 2 adsorption capacity. High CO 2 concentration favors the CO 2 adsorption capacity and rate as concentrated CO 2 favors the CO 2 diffusion in the pore space of the adsorbent, enhances the interaction between CO 2 and surface amine groups. The dry CO 2 adsorption capacity of AHTSA increases from 1.64, 4.19 to 6.66 mmol/g when the CO 2 concentration of the mixture gas varies from ∼400 ppm (air), 1% to 10%. Short adsorption halftime and high amine efficiency of AHTSA with different CO 2 concentrations reveal that AHTSA is a dynamic and effective adsorbent for CO 2 capture, even direct air capture. [ABSTRACT FROM AUTHOR]