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A new nanoporous material consisting of nano-ZnO particles bridged by –O–Si–O–Si–O– units has been synthesized and characterized. The two-step synthesis involves a precipitation of zinc oxide from a 1 mol l−1 methanolic zinc acetate solution with methanolic KOH in the presence of alkoxyalkylsilanes as coating agents and a UV irradiation of the obtained material in aqueous suspension with air supply. This procedure leads to a nanoscale ZnO network with a high surface area (130 m2 g−1), a better chemical stability than other types of ZnO and a remarkable photocatalytic activity. The photocatalytic mineralization of tetrachloroethylene occurs in the presence of this material at pH = 8 even faster than with the well known and most appreciated nano-TiO2 (anatase).

An intimate mixture of CuO/ZnO nanocrystals was prepared by an easy sol-gel synthesis (precipitation in methanol by hydroxide in the presence of a silane). The organic substituents of the silane were almost completely removed by a subsequent photochemical oxidation. The resulting amorphous SiO 2 prevented the growth of the catalytically active particles to larger crystals. The coating layer of silica can easily be penetrated by gaseous reactants, as shown by the high spe-

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