Electrochemistry of Zeolite-Associated Species

From the seminal work of Lunsford et al. in the early 1980s (DeWilde et al., 1980 Quayle and Lunsford, 1982), ship-in-a-bottle synthesis of metal complexes in the zeolite supercages, encapsulation of catalytically, optically, and/or electrochemically active species within micro- and mesoporous aluminosilicates, has received considerable attention (Alvaro et al., 2003). Site isolation of individual guest molecules, combined with shape and size restrictions imposed by the supercage steric limitations. 

Let us consider the electrochemical reduction of the oxidized form of an electroactive species. The extrazeolitic mechanism involves two steps first, the zeolite-associated electroactive species is ion-exchanged with electrolyte cation, M  

In these equations, (sol) denotes solvated species in electrolyte solution and species attached to the zeolite framework. 

The intrazeolitic mechanism involves the reduction of intrazeolite species coupled with the ingress of charge-balancing electrolyte cations into the zeolite framework  

To elucidate reaction pathways, several experimental features have to be considered (Bessel and Rolison, 1997a Domenech et al., 2002a, 2003a, 2004e)  

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