Porous carbon frameworks with high CO2 capture capacity derived from hierarchical polyimide/zeolitic imidazolate frameworks composite aerogels

Zeolitic imidazolate frameworks (ZIF) are widely regarded as promising materials for CO2 capture and storage because of their high specific surface areas and ordered pore structures. However, ZIF are manufactured as a fine powder, and as a result it is often challenging to process them efficiently into functional materials for practical application. Therefore, the objective of this work is to demonstrate a facile direct mixing, supercritical CO2 drying, and carbonization process for preparing a novel porous carbon materials based on polyimide/ZIF (PI/ZIF) composite aerogels. An interesting finding is that the organometallic frameworks are unstable and can collapse as mixing with the polyamic acid (PAA) solution due to the strong complexation between carboxyl group in polyamic acid chains and metal ions, which shows a great effect on the microporous structure of PI/ZIF composite aerogels. Accordingly, the resultant carbon aerogels displayed a complex hierarchical porous structure, which can be altered via ZIF loading amount (up to 20 wt%) and type of ZIF used. Although the CO2 capture performance of as-prepared PI aerogels was not significantly improved via the direct addition of ZIF, subsequent carbonization resulted in dramatic enhancements at concentrations above 10 wt% of ZIF, reaching up to 50 cm(3)/g (2.23 mmol/g, 298 K). Overall, we report a direct production process for preparing hierarchical PI aerogels which can be further carbonized for enhanced CO2 capture performance, demonstrating their practical functionality for CO2 adsorption.