Preparation and Characterization of Polyimide Aerogels with a Uniform Nanoporous Framework

Polyimide (PI) aerogels were successfully synthesized via a straightforward sol-gel process under room temperature along with the supercritical CO₂ drying method using 4-amino-N-methylbenzamide and 3,3′,4,4′-biphenyltetracarboxylic dianhydride. 1,3,5-Triaminophenoxybenzene was used as the cross-linker. The chemical structure, pore structure, morphology, thermal performance, CO₂ adsorption, and mechanical performance of PI aerogels were investigated. The as-prepared PI aerogels had low bulk densities (0.091-0.167 g/cm³), low shrinkages (9.73-17.36%), low thermal conductivities (0.0307-0.0341 W/m·K), high specific surface areas (449.76-538.19 m²/g), small pore diameter (10.37-22.41 nm), high thermal stability (onset of decomposition above 560 °C), and excellent mechanical property. The CO₂ adsorption capacities of PI aerogels were substantially higher than the values of the previous porous materials reported under the similar conditions, and the CO₂ uptake capacity was as high as 31.19 cm³/g at 25 °C and 1.0 bar. The resulting PI aerogels could be potentially used as thermal insulators and CO₂ adsorbents.