An ab initio study of the CH2O adsorption on the MgO (100) surface. Effects of replacing the active Mg ion by different metallic cations

A theoretical analysis of the interaction between formaldehyde, CH₂O, and the MgO (100) surface is reported. Ab initio Hartree-Fock calculations are carried out using an embedded cluster approach in which the environment is described by both total ion potentials and point charges. The cluster selected to describe the CH₂O-surface interaction is CH₂OMgO₅]⁸⁻, in which the formaldehyde oxygen is coordinated to the Mg²⁺ ion. The effect of the addition of metallic cations to the catalyst is analysed by replacing the cluster Mg²⁺ ion by Na⁺, Al³⁺, Sc³⁺ and Ti⁴⁺ so as to modify the Lewis acid properties of the surface. The different contributions to the adsorbate-surface interaction are analysed, and the theoretical vibrational frequencies are discussed.