Adsorption of methanol on cationic cobalt clusters in the gas phase

Knowledge about the adsorption and activation of methanol on metal catalysts is essential to obtain insights into the conversion of methanol to sustainable chemicals. In this work, the adsorption of methanol on Co_n⁺ (n = 1-60) clusters is investigated using low-pressure collision cell experiments in combination with time-of-flight mass spectrometry. Experiments are conducted using both methanol and deuterated methanol in order to examine potential isotope effects and to gain insights into the reaction mechanism. Kinetic data and Rice-Ramsperger-Kassel-Marcus calculations indicate the absence of methanol desorption for n < 10 cluster sizes, suggesting dissociative chemisorption of methanol for those sizes. For larger clusters, the reaction involves a combination of association and desorption, with a pronounced size dependence of the corresponding reaction rates. This size dependence is anti-correlated with the promotion energy of an electron from an occupied frontier orbital to the lowest unoccupied d-state.