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

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.