DFT-ONIOM study of ammonia activation by MM'APO-5 (M,M' = Ti, Zr, Co) bimetallic molecular sieves. The influence of the neighboring metal from a theoretical point of view

Abstract:

ONIOM-DFT calculations have been carried out in order to determine how the neighboring metal influences the activation free energies (ΔG^≠) and the mechanisms of NH<inf>3</inf> activation in a series of mono and disubstituted aluminophosphates MM'APO-5, (M, M’ = Co, Ti Zr). The results revealed that metal clustering is thermodynamically favorable (ΔG < 0) for all MAPO-5s and MM'APO-5s studied here. The aluminophosphates TiAPO-5 and ZrAPO-5 are unable to activate NH<inf>3</inf> due to their inability to stabilize the key intermediate M–NH<inf>2</inf>. The calculated activation free energy values (ΔG^≠) suggest that CoZrAPO-5 is better suited for NH<inf>3</inf> activation, as its values are lower than those of CoTiAPO-5 in the mechanism studied.

Año de publicación:

2024

Keywords:

• CoTiAPO-5
• DFT
• ONIOM
• TiAPO-5
• ZrAPO-5

Fuente:

scopus