Investigations on the reactions of uranium oxide molecules with CO offer new inspiration for the design of promising high-efficiency catalysts for CO activation using actinide materials. Herein, we contribute a combined matrix-isolation infrared spectroscopic and theoretical study of CO oxidation to CO 2 on uranium dioxide (UO 2 ) molecules in solid argon. The reaction intermediate O 2 U(η 1 -CO) is generated spontaneously at the bands of 1893.0, 870.6, and 801.3 cm −1 during codeposition and annealing. Upon the following irradiation, CO 2 is substantially produced by the consumption of O 2 U(η 1 -CO), indicating the catalytic conversion of CO to CO 2 through the intermediate O 2 U(η 1 -CO). In C 18 O isotopic substitution experiments, the yields of 16 OC 18 O convincingly confirm that one of the oxygen atoms in CO 2 derives from UO 2 . The reaction pathways are discussed based on the theoretical and experimental results.

Fundamental investigation of metal–CO interactions is of great importance for the development of high-performance catalysts to CO activation. Herein, a series of side-on bonded mononuclear lanthanide (Ln) oxocarbonyl complexes OLn(η2-CO) (Ln = La, Ce, Pr, and Nd) have been prepared and identified in solid argon matrices. The complexes exhibit uncommonly low C–O stretching bands near 1630 cm–1, indicating remarkable C–O bond activation in these Ln analogues. The η2-CO ligand in OLn(η2-CO) can be claimed as an anion on the basis of the experimental observations and quantum chemistry investigations, although the CO anion is commonly considered to be unstable with electron auto-detachment. The CO activation in OLn(η2-CO) is attributed to the photoinduced intramolecular charge transfer from LnO to CO rather than the generally accepted metal → CO π back-donation, which conforms to the traditional Dewar–Chatt–Duncanson motif. Energy decomposition analysis combined with natural orbitals for chemical valence calculations demonstrates that the bonding between LnO and η2-CO arises from the combination of dominant ionic forces (>76%) and normal Lewis “acid–base” interactions. The fundamental findings provide guidelines for the catalyst design of CO activation.