The nonporous ([(Bu)4N]4[ホウ-SiW10O34(H2O)2]ツキH2O, 1.H2O) synthesized through a bottom-up approach sorbs EtOAc, which is highly mobile in the solid bulk of the compd., probably contributing to the easy co-sorption of olefins and H2O2. 1 Heterogeneously catalyzes size-selective oxidn. (small olefins are much more preferentially epoxidized than large olefins) of various org. substances including olefins, sulfides, and silanes with aq. H2O2 in EtOAc. 1 Can easily be sepd. by filtration and reused several times with retention of its high catalytic activity and is the 1st example for the heterogeneously catalyzed size-selective liq.-phase oxidn. with H2O2 by a POM-based catalyst. [on SciFinder(R)]