Influence of aluminium distribution on the diffusion mechanisms and pairing of [Cu(NH3)2]⁺ complexes in Cu-CHA

Journal article, 2025

The performance of Cu-exchanged chabazite (Cu-CHA) for the ammonia-assisted selective catalytic reduction of NOx (NH3-SCR) depends critically on the presence of paired formula presented complexes. Here, a machine-learning force field augmented with long-range Coulomb interactions is developed to investigate the effect of Al-distribution and Cu-loading on the mobility and pairing of formula presented complexes. Performing unbiased and constrained molecular dynamics simulations, we obtain unique information inaccessible to first-principle calculations and experiments. The free energy barrier for formula presented diffusion between CHA-cages depends sensitively on both the local and distant Al-distribution. Importantly, certain Al-distributions and arrangements of neighboring formula presented cations make paired formula presented complexes exothermic with respect to separated configurations. Our results suggest that the NH3-SCR activity can be enhanced by increasing the Cu-loading and Al-content. The dynamic interplay between formula presented diffusion is crucial for the formula presented mobility and stresses the need to explore large systems including long-range Coulomb interactions when studying diffusion of charged species in zeolites.