CO₂ Versus CH₄ Aggregation on Trifluorobenzene: Molecular Level Characterization via Rotational Spectroscopy

Abstract

AbstractThe cluster growth behavior of CO2 and CH4 on an aromatic ligand has been studied through the unambiguous identification of complex structures of 1,2,3‐trifluorobenzene‐(CO2)1–4 and ‐ß(CH4)1–2 using broadband rotational spectroscopy in conjunction with extensive theoretical calculations. The results reveal a contrast in the thermodynamically favorable ligand‐gas binding sites and noncovalent interactions of the two gaseous molecules on the ligand. The observation of a tunneling splitting and large centrifugal distortions indicates that CH4 molecules bind to the fluorinated π system via three weak hydrogen bonds without CH4 self‐interactions, resulting in an effective structure displaced toward the dissociation limit. Conversely, CO2 shows diverse and stronger intermolecular interactions with the fluorinated benzene, including F─C tetrel bonding, lone pair to π‐hole interactions, π–π stacking, and a significant contribution from CO2 self‐interactions. The thorough examination of ligand–gas interactions and aggregation patterns highlights the significant capacity and selectivity of the fluorinated aromatic ligand for accepting CO2 over CH4.