Structural Study of [Sc₃O₄(CO₂)]⁺ (n = 2, 3) Complexes by Infrared Photodissociation Spectroscopy and Density...

The catalytic transformation of CO₂ into valuable products has garnered wide interest owing to both economic and environmental benefits, in which the chemical fixation of CO₂ into carbonate structures represents a crucial step that occurs on the adsorbed catalyst surfaces. Transition metal oxides with acidic and basic active sites have exhibited potential in promoting the carbonation of weakly bound CO₂ molecules. Here, the interactions between CO₂ molecules and the Sc₃O₄⁺ cation in the gas phase are investigated by using infrared photodissociation spectroscopy in conjunction with quantum chemical calculations. Both end-on and various carbonate-containing configurations, including center and bridge carbonate structures, have been theoretically identified for the CO₂-coordinated ion-molecule complexes. Based on the comparison between the experimental spectra and simulated spectra of low-lying isomers in the CO₂ antisymmetric stretching vibrational frequency region, isomers characterized by a bridge carbonate core structure are demonstrated to be the major contributors to the observed spectra. Examination of potential energy surfaces reveals lower energy barriers and simpler reaction routes for the conversion of molecularly bound CO₂ into a bridge carbonate moiety, providing reasonable explanations for their prevalence in the experiments.