Water-insoluble Ag-U-organic assemblies with photocatalytic activity

Two metal-organic coordination polymers [Ag(bipy)(UO2)(bdc)(1.5)] (bipy = 2,2'-bipyridyl, bdc = 1,4-benzenedicarboxylate) and [Ag-2(phen)(2)UO2(btec)] (phen = 1,10-phenanthroline, btec = 1,2,4,5-benzenetetracarboxylate) were obtained by hydrothermal assembly of the d(10) metal silver and the 5f metal uranium with mixed ligands. Both compounds form two-dimensional networks with pi-pi overlap interactions between the aromatic fragments in the neighboring layers. In aqueous suspension the two water-insoluble materials show photocatalytic degradation performance superior to that of commercial TiO2, (Degussa P-25) when tested on nonbiodegradable rhodamine B (RhB) as model pollutant. The relationship between the structure of the photocatalysts and the photocatalytic activity was also elucidated. On the basis of the monitored intermediate species and the final mineralized products, it is proposed that the possible reaction mechanism for the photodegradation (oxidation) of RhB in aqueous solution catalyzed by the two assembly compounds involves photoexcitation of uranyl centers and molecular oxygen.