Photon Factory Activity Report 2016 #34 (2017)

BL-5A/2016G677

The Intrazeolitic Chemistry of Silver
Nam Ho Heo1,*, Yang Kim2, Jong Jin Kim3, and Karl Seff4
Laboratory of Structural Chemistry, Department of Applied Chemical Engineering, Kyungpook NationalUniversity, Daegu 41566, Korea
2
Department of Chemistry, College of Natural Science, Busan National University, Busan 46241, Korea
3
Department of Earth System Science, College of Natural Science, YonSei University, Seoul 03722, Korea
4
Department of Chemistry, University of Hawaii, 2545 The Mall, Honolulu, Hawaii 96822, U. S. A
1

1 Introduction
The void space of a zeolite is a medium, like space or asolvent, in which a chemistry can occur. Unlike thosemedia, however, because a zeolite is a crystalline solid,
the detailed structure of the product of a reaction orprocess can be observed crystallographically to relatively
high precision. Accordingly, crystallography, especiallysingle crystal crystallography, is a powerful method forthe study of intrazeolitic chemistry.
Ag+ has a particular affinity for zeolites, it exchanges
easily and quantitatively into them from aqueous solution,
usually replacing Na+ ions. For a variety of reasons
including uptake of anions, incomplete exchange, andcation hydrolysis (which can lead to partial H+ exchange
and, in turn, crystal damage), this cannot be said of mostcations. Ag+ has none of these problems.
2 Experiment
To do an experiment in zeolite chemistry, the first stepis usually to replace the exchangeable cations, usually
Na+, in the zeolite as it was synthesized with other cations,whichever ones one wants to study. That is generally
done from aqueous solution. The second step (unless theobjective is just to study the hydrated zeolite) is todehydrate the zeolite to get the water out of the way. It is
generally the dehydrated zeolite that has utility incatalysis and sorption. Also, other molecules of interest
can be sorbed into an empty zeolite and those sorption
structures can be learned. If those other molecules react,
the reaction products can be seen. More complex steps ofion exchange, dehydration, and the sorption of more
substances, all for various times and at various
temperatures, may be used.
3 Results and Discussion
New small molecules and cations have beensynthesized within silver containing zeolites, and theirstructures were determined using single crystal
crystallography. Some of them are the hydronitrogens
N3H5 and cyclo-N3H3[1], octahedral Ag6[2], and the silver
halide clusters Ag4Cl4[3], Ag4Br4[4], and Ag4I4[5]. Thesilver halide clusters within their zeolites are ordered
three-dimensional arrangements of identical quantum dots.
The (C3O3H3)22+ cation, a reduced dimer of C3O3H33+(tripyrylium) is seen[3]; tripyrylium is planar andisoelectronic with benzene. The two rings bond together
facially via their π* orbitals in an eclipsed manner with avery short interplanar distance, 2.43 Å. Several examplesof silver containing zeolites are presented to Fig. 1, 2, and3.
Molecules formed within a zeolite may be stable only
within the zeolite; it may not be possible to isolate them.
While such isolation should be possible for only N3H5
and perhaps cyclo-N3H3, we do not easily foresee this tobe the case for the other species.

3+Fig. 1: N3H5, cyclo-N3H3, and C3O3H3Fig. 2: Hexasilver molecule, A60, in a sodalite cavity

Fig. 3: Ag4Cl4 cluster in a sodalite cavity

References[1] Y. Kim. et al., J. Am. Chem. Soc 99, 7057 (1977).
[2] Y. Kim et al., J. Am. Chem. Soc 99, 7055 (1977).
[3] S. H. Kim. et al., J. Phys. Chem. C 112, 11181 (2008).
[4] W. T. Lim. et al., Bull. Korean Chem. Soc 26, 1090
(2005).
[5] N. H. Heo. et al., J. Phys. Chem. B 108, 3168 (2004).
* nhheo@knu.ac.kr