Effect of the Al Siting
on the Structure of Co(II)
and Cu(II) Cationic Sites in Ferrierite. A Periodic DFT Molecular
Dynamics and FTIR Study
Stepan Sklenak
Prokopis C. Andrikopoulos
Sarah R. Whittleton
Hana Jirglova
Petr Sazama
Lubomir Benco
Tomas Bucko
Juergen Hafner
Zdenek Sobalik
10.1021/jp310236d.s001
https://acs.figshare.com/articles/journal_contribution/Effect_of_the_Al_Siting_on_the_Structure_of_Co_II_and_Cu_II_Cationic_Sites_in_Ferrierite_A_Periodic_DFT_Molecular_Dynamics_and_FTIR_Study/2439442
Periodic DFT molecular dynamics and FTIR spectroscopy
were used
to investigate the cationic sites of ferrierite exchanged with Co(II)
and Cu(II) and their complexes with NO. Particular attention was paid
to the effect of the Al siting in six-membered rings forming the cationic
sites on the structure of these sites and the corresponding binding
energies of Me(II) (Me = Co and Cu). Our calculations show that both
the cations upon binding to cationic sites induce a rearrangement
of the local structure of the zeolite framework. The rearrangement
is significant for the α and β-2 sites while it is minor
for the β-1 site. Comparison of the observed and theoretical
NO stretching frequencies of ferrierite Co(II) and Cu(II) complexes
with a NO molecule permitted the assignment of IR bands to the individual
types of cationic sites. For NO-Co-ferrierite, the IR bands found
at 1956, 1941, and 1935 cm<sup>–1</sup> can be assigned to
NO-Co complexes with Co(II) located in the α, β-1, and
β-2 sites, respectively. Similarly for NO-Cu-ferrierite, the
frequencies of 1864, 1912, 1904, and 1892 cm<sup>–1</sup> belong
to NO-Cu complexes having Cu(II) accommodated in the α, β-1,
β-2 (conformer 1), and β-2 (conformer 2) sites, respectively.
The calculated adsorption energies are systematically higher for Co(II)
than for Cu(II) for all the three sites and are in the order α
> β-2 > β-1 for both the cations. Our computational
results
further reveal that upon binding Me(II) both the local structure of
the zeolite framework as well as the binding energies of Me(II) strongly
depend on the Al siting in the rings forming the cationic sites. The
calculated relative binding energies of Me(II) are in the order β-1
> β-2 > α for both the cations. The general tendency
of
Me(II) accommodated in a cationic site to react is inversely proportional
to the corresponding binding energies. We also showed that FTIR spectroscopy
of complexes of NO and Me(II)-exchanged ferrierite can serve to identify
the Al siting in the six-membered rings forming cationic sites.
2016-02-19 20:56:50
zeolite framework
Co
FTIR spectroscopy
Al siting
FTIR StudyPeriodic DFT
IR bands
Periodic DFT Molecular Dynamics
Cu
complex
cationic sites
binding energies