Surprising Intrazeolitic Chemistry of Silver

Abstract

New small molecules and cations have been synthesized within silver-containing zeolites, and their structures were determined using single-crystal crystallography. Some of them are the hydronitrogens N3H5 and cyclo-N3H3, octahedral Ag6, and the silver halide clusters Ag4Cl4, Ag4Br4, and Ag4I4. The silver halide clusters within their zeolites are ordered three-dimensional arrangements of identical quantum dots. The (C3O3H3)22+ cation is a reduced dimer of C3O3H33+ (tripyrylium); tripyrylium is planar and isoelectronic with benzene. The two rings bond together facially via their π* orbitals in an eclipsed manner with a very short interplanar distance, 2.43 Å. When a hydrated silver-exchanged zeolite is heated (to dehydrate it), Ag+ ions react with framework oxygen atoms to give silver atoms and O2(g); this leads to crystal damage and the complete loss of crystalline diffraction. This damage, however, can be repaired and the diffraction fully restored by heating in O2(g). To avoid crystal damage altogether, silver-exchanged zeolites can be dehydrated at elevated temperatures in flowing O2(g).