Local intermolecular interactions for selective CO₂ capture by zeolitic imidazole frameworks: energy decomposition analysis

Abstract

Intermolecular energy decomposition analysis (EDA) is reported for the binding of CO₂ with zeolitic imidazole frameworks (ZIF) to provide a molecular level interpretation of the recent capacity and selectivity measurements of several ZIFs and to suggest a theoretical guideline to improve their performance further, using 1 nm size of organic linker fragment of the ZIFs as a target molecule. The EDA suggests that the local electronic interaction of CO₂ and the substituent groups, mainly frozen density and polarization interactions with little charge transfer, is the primary binding interaction, but the electron correlation effects can be equally or more important depending on the binding geometry and functional groups. The present correlated calculations identify the preferred ZIF binding sites for various gases including CO₂ to be mostly near the benzene substituent groups rather than the plane of imidazole rings. We predict that the NH₂-substituted ZIF would have an enhanced capacity of CO₂ as compared to the NO₂-substituted ZIF that was recently synthesized and reported to be one of the materials with the best capacity results along with high gas selectivity. The present calculations may imply that the local functionality of the linking organics, rather than detailed framework structures, may be of primary importance in designing certain high capacity MOF or ZIF materials.

This article is part of the Topical Collection on Nanotechnology for Sustainable Development