Identifying free energy landscapes of proton transfer processes between Bronsted acid site and water clusters inside the zeolite pores
writer：Peng Liu, Donghai Mei
keywords：Molecular dynamics simulations, catalytic reactions
source：期刊
specific source：Journal of Physical Chemistry C, 2020, DOI: 10.1021/acs.jpcc.0c07033
Issue time：2020年
In the aqueous phase zeolite-catalyzed reactions, water molecules profoundly alter the reaction activity and reaction mechanisms. This can be ascribed to the changing nature of Br?nsted acid site (BAS) induced by surrounding water molecules. In this work, the effects of water clusters with different sizes on the BAS site were investigated using ab initio molecular dynamics simulations combined with enhanced sampling methodology. The proton hopping processes between the BAS site and the water cluster or within the water cluster have been mapped out with free energy landscapes. As H 2 O/BAS ratio equals to 1, the proton hops between two oxygen atoms of the BAS site. As H 2 O/BAS ratio is 2, the proton prefers to shuttle between the zeolite framework and the water dimer. As H 2 O/BAS ratio reaches 3, the proton moves away from the BAS site to the linear water trimer, and shuttles between oxygen atoms within the water cluster chain. The increasing proton affinity with the expanding water cluster size can be attributed to the enhanced electron density at oxygen atoms of the water cluster.