Multiscale investigation of CO₂ capture in 1,2,4-triazolium-based ionic liquids and porous copolymers using density...

Capturing carbon dioxide (CO₂) directly from the atmosphere has become an essential approach in efforts to address climate change, particularly within broader carbon capture and storage frameworks. Among the materials explored for direct air capture, ionic liquids (ILs) stand out as their chemical structure can be finely adjusted to optimise how they interact with CO₂, including both capture and subsequent transformation. Building on this concept, poly(ionic liquid)s (PILs) have been developed as an advanced class of materials that provide greater structural stability and enhanced interaction sites, leading to more efficient CO₂ uptake. This study investigates the CO₂ capture performance of six 1,2,4-triazolium-based ILs and their corresponding porous copolymers, using a combined density functional theory (DFT) and all-atom molecular dynamics (MD) simulation approach. The DFT calculations show that CO₂ adsorption is mainly governed by noncovalent interactions with the anions, while the functional groups attached to the 1,2,4-triazolium cations strongly influence the adsorption strength by increasing the availability of electron-rich interaction sites, as consistently evidenced by molecular electrostatic potential (MESP) analysis. The frontier molecular orbital (FMO) analysis and quantum theory of Atoms-in-molecules (QTAIM) analysis confirms that these functional groups do not merely contribute sterically but actively modulate the electronic distribution responsible for stabilizing the adsorbed CO₂ molecules. MD simulations complement these results by capturing bulk thermodynamic and transport properties under realistic conditions. This integrated multiscale framework provides a comprehensive understanding of 1,2,4-triazolium-based sorbents and guides the rational design of next generation materials for efficient, regenerable, and scalable CO₂ capture applications.