Comparative theoretical study of Au_1-3 and Cu_1-3 clusters supported on SAPO-11 and their interactions with CO

Quantum chemistry calculations were carried out using the ONIOM2 methodology at two different levels of calculation, B3LYP for the high level and UFF for the low level. These calculations were performed on aggregates to analyze the geometries of small clusters of Au_1-3 and Cu_1-3 supported on SAPO-11. Similarly CO-Au_1-3/SAPO-11 and CO-Cu_1-3/SAPO-11 moieties obtained by their interaction with CO, were calculated and the results of both cases are compared. The formation energy ΔE_F of the metal aggregates and with CO adsorption, C-O and M-CO bond distances and calculated CO stretching frequencies are reported.The most stable structures of the aggregates of Au_1-3 and Cu_1-3/SAPO-11 are similar, Au₃ exhibits acute triangle geometry and Cu₃ shows isosceles triangle with a large side geometry. The CO ΔE_ads values reveal that the CO adsorption is more stable in Au_1-3/SAPO-11 than in Cu_1-3/SAPO-11. Au-CO distances are larger than Cu-CO.