CO interaction with Cu(I)-MCM-22 zeolite: density functional theory investigation

Abstract

MCM-22 zeolite has been widely used in many applications for catalysis and adsorption. Especially, this material exchanged with Cu⁺ cation (Cu(I)-MCM-22) is an active catalyst in green chemical reaction, such as decomposition of NO and N2O. The local geometry of Cu⁺ in vicinity of Al (III) replacement in six different Si (IV) sites and CO interaction with the most stable Cu⁺ in each Al site were explored using periodic density functional theory (DFT) method. The CO stretching frequencies were computed applying the ω/r scaling method in which frequencies were determined at high quantum level (couple cluster) and CO bond length calculated at DFT level. The results showed that Cu⁺ cation located in the channel wall position and intersection position coordinated with 3 or 2 framework oxygen atoms, respectively, before CO adsorption and Cu⁺ cation coordinated with 2 framework oxygen atoms after CO adsorption. The interaction energies between CO and Cu+ cation were in range - 148 to -195 kJ.mol^-1 and CO frequencies exhibit two peaks at 2151 and 2159 cm^-1 in good agreement with experimental data. This investigation brought us to understand the Cu⁺ location in MCM-22 and CO adsorption in Cu(I)-MCM-22 zeolite.