Revisiting MgO–CO surface chemistry: an IR investigation

Abstract

The first product formed upon interaction of CO with the surface of fully dehydroxylated MgO is CO^2–₂. This species is generated by nucleophilic attack of a surface O^2– on CO weakly σ-bonded on an Mg²⁺ cation in an adjacent position. The CO^2–₂ species generates C₃O^2–₄ by addition of 2 CO molecules. Trimeric species (and unreacted CO^2–₂) are the most abundant components at 77 K. Further addition of CO molecules at room temperature generates oxygen-sensitive C_2nO^2–_{(2n+ 1)} species which have an open structure and are responsible for the pink colour of the sample. Long exposure at room temperature, and moderate increase of temperature, favour disproportionation reactions, leading to adsorbed CO₂(CO^2–₃) and C.