Adsorption of dioxygen to copper in CuHY zeolite

Abstract

The adsorption of dioxygen to copper in CuHY zeolites has been studied by means of FTIR spectroscopy and model calculations at the quantum mechanical/molecular mechanics (QM/MM) level. Different Si/Al ratios, substitution patterns and adsorption sites within the cavities of the zeolite lead to a large number of different isomers to be studied. In addition, these parameters control the end-on vs. side-on adsorption of dioxygen. High-level multireference benchmark calculations for the singlet and triplet states of such adsorption complexes corroborate the use of density functional theory for the investigation of these systems. Comparison of the experimental and computed data allows for the identification of a preferred adsorption site and a small number of isomers which appear to be most relevant for the adsorption process. Redshifts of >250 cm(-1) are obtained for the vibrational frequencies of adsorbed O(2).

Selective Catalytic Oxidation of CH Bonds with Molecular Oxygen

“…An alternative approach attempts a complete understanding of the elementary catalytic step on a molecular level based on spectroscopic, kinetic and quantum chemical methods, permitting an intentional variation of the catalytic parameters. A series of investigations in this direction was conducted with Cu/HY and Cu/HZSM‐5 zeolites 11, 232–236…”

“…Copper is a classical O 2 activating element with mono‐, di‐ and multi‐Cu centers in enzymes 10. Mono‐Cu centers can bind O 2 end‐on or also side‐on , depending on the environment 11. Biomimetic analogs of these centers have been modeled in zeolites12 and investigated by DFT quantum chemical calculations (Figure 1, Table 1).…”

A Facile Route toward the Increase of Oxygen Content in Nanosized Zeolite by Insertion of Cerium and Fluorinated Compounds

“…Upon its adsorption on zeolite, the IR silent O–O stretching mode of molecular oxygen becomes active at 1556 cm −1 [ 6 , 30 , 31 , 32 ]. The prepared zeolites show a band centered at 1553 cm −1 ( Figure 5 , Figures S3 and S4 ) which is in the same region of the reported values at 1553 and 1557 cm −1 (shoulder) corresponding to O 2 adsorbed on the Brønsted and on the Na sites, respectively [ 6 , 33 ].…”

Electronic Effects in Organic Chemistry

“…In these studies, the QM part typically includes the metal and these parts of the system which are directly involved in the reaction. We also want to mention some work which was performed by Sierka, Sauer and co-workers [37,39,694,695]. This review highlights pure QM investigations for the (1,2)-asymmetric induction in the nucleophilic addition to chiral carbonyl compounds and the proline-catalyzed asymmetric aldol reaction.…”