Intrazeolite nonstoichiometric tungsten oxides n[WO{sub 3-x}]-Na{sub 56}Y (O < n {le} 32, O {le} x {le} 1)

Abstract

The photooxidation of {alpha}-cage encapsulated n[W(CO){sub 6}]-Na{sub 56}Y, where O < n {le} 16 and Na{sub 56}Y denotes sodium zeolite Y, provides a mild, clean, and quantitative synthetic pathway to molecular dimension tungsten (VI) oxide moieties, encapsulated within the void structure of the zeolite Y host, according to the reaction stoichiometry n[W(CO){sub 6}]-Na{sub 56}Y+9/2nO{sub 2}{r_arrow}n[WO{sub 3}]-Na{sub 56}Y+6nCO{sub 2}. Following photooxidation, half of the {alpha}-cage void volume in the Na{sub 56}Y host is freed so that subsequent precursor (saturation level) impregnations/photooxidations can be carried out in a stepwise fashion, proceeding as n = 16, 24, 28, 30, ..., 32 per unit cell. Thermal vacuum treatment of these materials proceeds in two well-defined steps around 300 and 400 {degrees}C to yield encapsulated n[WO{sub 3-x}]-Na{sub 56}Y materials having x = 0.5 and 1, respectively. This reduction process is reversible by heating in an O{sub 2} atmosphere at 300 {degrees}C. 34 refs., 14 figs., 2 tabs.