Denitrification mechanism of low temperature NH₃-SCR based on Cu-based catalysts

The dynamic movement of the NH₃-solvated Cu site in Cu-CHA zeolite is a unique phenomenon connecting heterogeneous catalysis and homogeneous catalysis,and is the most promising and advanced catalyst for ammonium-assisted selective reduction of nitrogen oxides（NH₃-SCR） technology in diesel exhaust post-treatment. Firstly,recent theoretical advances in low-temperature copper dynamics were summarized,and the evidence for the movement of copper atoms in and between cages resulting from molecular dynamics（AIMD） or kinetic simulations was highlighted. Synchrotron X-ray spectroscopy,vibrational and optical techniques,including diffuse infrared Fourier Transform spectroscopy（DRIFTS） and diffuse ultraviolet-visible spectroscopy（DRS）,electron paramagnetic spectroscopy（EPR） and impedance spectroscopy（IS）were combined to track evolution of Cu coordination and local structure during low-temperature NH3-SCR. The role of copper dynamics in tuning redox properties,preparing highly dispersed Cu-CHA via solid-state ion exchange and in situ monitoring of NH₃ storage and conversion was elucidated. Mechanistic insights provide new strategies for enhancing low-temperature NH₃-SCR efficiency and extend to other metal-exchanged-zeolite reactions.