Extension of BET theory to CO2 adsorption isotherms for ultra-microporosity of covalent organic polymers

• Main Authors: Mukhtar, A., Mellon, N., Saqib, S., Lee, S.-P., Bustam, M.A.
• Format: Article
• Published: Springer Nature 2020
• Online Access: https://www.scopus.com/inward/record.uri?eid=2-s2.0-85096140500&doi=10.1007%2fs42452-020-2968-9&partnerID=40&md5=f808294fa5ef668716429abfa6b9a5cc; http://eprints.utp.edu.my/23253/

Usually, nitrogen and argon adsorption�desorption isotherms are used at their respective boiling points for the determination of specific surface area via the BET theory of microporous materials. However, for ultra-micropores, where nitrogen and argon cannot access at cryogenic temperatures, the CO2 adsorption�desorption isotherms have been considered as alternative options for the determination of specific surface area by extending BET theory, but the surface area determined by using CO2 adsorption�desorption isotherms is not significant due to strong CO2-CO2 interactions. In this study, the microporous covalent organic polymers are subjected to nitrogen and CO2 adsorption�desorption isotherms and the results showed that a clear linear region is available in isotherms, which confirms the presence of ultra-micropores. The surface area determined by the CO2 adsorption�desorption isotherms is higher than the surface area determined by N2 adsorption�desorption isotherms. These results indicate that the microporous covalent organic polymers contain ultra-micropores where only CO2 can reach, while nitrogen and argon cannot access at cryogenic conditions because their kinetic diameter is larger than CO2. © 2020, Springer Nature Switzerland AG.