Critical Role of Dynamic Flexibility in Ge-Containing Zeolites: Impact on Diffusion.
Incorporation of germanium in zeolites is well known to confer static flexibility to their framework, by stabilizing the formation of small rings. In this work, we show that the flexibility associated to Ge atoms in zeolites goes beyond this static effect, manifesting also a clear dynamic nature, in the sense that it leads to enhanced molecular diffusion. Our study combines experimental and theoretical methods providing evidence for this effect, which has not been described previously, as well as a rationalization for it, based on atomistic grounds. We have used both pure-silica and silico-germanate ITQ-29 (LTA topology) zeolites as a case study. Based on our simulations, we identify the flexibility associated to the pore breathing-like behavior induced by the Ge atoms, as the key factor leading to the enhanced diffusion observed experimentally in Ge-containing zeolites.
Department Physical, Chemical and Natural Systems, Univ. Pablo de Olavide, Ctra. de Utrera km. 1, 41013, Seville, Spain.
Juan José
JJ
Gutiérrez-Sevillano
Department Physical, Chemical and Natural Systems, Univ. Pablo de Olavide, Ctra. de Utrera km. 1, 41013, Seville, Spain. scalero@upo.es.
Sofía
S
Calero
Department Physical, Chemical and Natural Systems, Univ. Pablo de Olavide, Ctra. de Utrera km. 1, 41013, Seville, Spain.
Said
S
Hamad
Department of Chemistry, University of Reading, Whiteknights, Reading, RG6 6AD, UK.
Ricardo
R
Grau-Crespo
Instituto de Tecnología Química, Universitat Politècnica de València-Consejo Superior de Investigaciones Científicas, Avenida de los Naranjos s/n, 46022, Valencia, Spain. frey@itq.upv.es.
Fernando
F
Rey
Instituto de Tecnología Química, Universitat Politècnica de València-Consejo Superior de Investigaciones Científicas, Avenida de los Naranjos s/n, 46022, Valencia, Spain.
Susana
S
Valencia
Instituto de Tecnología Química, Universitat Politècnica de València-Consejo Superior de Investigaciones Científicas, Avenida de los Naranjos s/n, 46022, Valencia, Spain.
Miguel
M
Palomino
Department Physical, Chemical and Natural Systems, Univ. Pablo de Olavide, Ctra. de Utrera km. 1, 41013, Seville, Spain.
Salvador R G
SR
Balestra
Department Physical, Chemical and Natural Systems, Univ. Pablo de Olavide, Ctra. de Utrera km. 1, 41013, Seville, Spain. rruisal@acu.upo.es.
A Rabdel
http://orcid.org/0000-0002-2004-687X
AR
Ruiz-Salvador
diffusion; flexibility; germanium; molecular modeling; zeolite