부산대학교 도서관

Polyoxotantalates, clusters of tantalum (Ta) oxide, are promising catalysts for CO2fixation reactions because of their exceptional Lewis basicity facilitating CO2activation. Here, we unveiled the CO2activation on [H2Ta6O19]6–(Ta6) by high-energy-resolution fluorescence-detection (HERFD) X-ray absorption near-edge structure (XANES). The white line of Ta L3-edge HERFD-XANES identified three peaks not discernible with conventional XANES. In situ HERFD-XANES study of CO2adsorption on Ta6showed the disappearance of the high-energy shoulder peak and the emergence of a new lower-energy peak. Theoretical calculations showed that the three peaks before CO2adsorption correspond to transitions to molecular orbitals with high contributions from Ta 5d orbitals split by the ligand field of the distorted Ohsymmetrical {TaO6} units. The observed peak replacement reflects both destabilization of the dx2–y2orbitals and stabilization of the dz2orbital induced by centering from the off-center arrangement of {TaO6} units by the CO2attachment on terminal oxygen.