Atomic and Electronic Structures of a Cu-exchanged Zeolite A

Cu-exchanged zeolites have attracted considerable attention as promising catalysts for reducing nitrogen oxides emissions and addressing environmental challenges associated with exhaust gas purification.In this study, the atomic structure of Cu-containing zeolite A (Cu-A) with a Cu/Al atomic ratio of 8.6 % was investigated by pair distribution function (PDF) analysis of highenergy X-ray diffraction data.Atomic dynamics were examined using high-resolution inelastic X-ray scattering.The measurements revealed Boson-peak-like excitations similar to glasses in both pure and Cu-A, with a slight reduction in intensity upon Cu incorporation.The Cu 3d partial density of states (pDOS) in the valence and conduction bands of this insulating material was determined by soft X-ray emission and absorption spectroscopies using Cu 2p-3d resonant excitation.The O 2p pDOS was similarly measured using O 1s-2p resonance.Density functional theory (DFT) calculations were also performed to clarify the atomic and electronic structures.Although the DFT calculations were limited to a relatively small simulation cell because of computational constraints, the calculated atomic PDF, Cu 3d pDOS, and O 2p pDOS showed good agreement with the experimental results.The calculated electronic charge distributions revealed partially filled Cu-derived states, which may be closely related to the catalytic functionality of this zeolite in exhaust gas purification.