Encapsulating Photoluminescent Materials in Zeolites. II. Crystal Structure of Fully Dehydrated Ce21H46O18–Y (Si/Al = 1.69) Containing Ce4O44+, CeOH2+, Ce3+, and H+

Encapsulating photoluminescent centers within zeolites may give them long-term stability and enhanced luminosity. A single crystal of zeolite Na–Y (FAU, Si/Al = 1.69) was fully exchanged with Tl+, then exchanged with Ce3+ and dehydrated at 623 K and 2 × 10–4 Pa to give |Ce4O44+3.5CeOH2+4.6Ce3+2.1H+41.7|[Si121Al71O384]–FAU. Its structure was determined crystallographically (space group Fd3̅m, a = 24.909(1) Å) with synchrotron X-radiation and was refined using all 1236 unique data to R1 = 0.067 (Fo > 4σ(Fo)) and R2 = 0.247. The 20.5 Ce3+ ions per unit cell occupy four crystallographically distinct cation sites: 0.5 are octahedral at site I, 1.6 trigonal at site I′, 13.8 octahedral at a second site I′, and 4.6 tetrahedral at site II. The 13.8 Ce3+ ions at the second site I′ are members of Ce4O44+ clusters, tetrahedrally distorted cubes occupying 43% of the sodalite cavities. Each of these Ce3+ ions bonds octahedrally to three oxygen atoms of the zeolite framework (2.482(7) Å) and to three extraframework oxide ions (2.521(11) Å). Those at site II are 4-coordinate; each bonds to three oxide atoms of the zeolite framework (2.420(7) Å) and to one hydroxide ion (2.06(14) Å). The ultaviolet photoluminescence spectrum of this material has a broad emission band between 320 and 400 nm, peaking at 347 nm.