Inorganic Ligand-Protected Synthesis and Characterization of {Ag6} Cluster within Annular Polyoxometalate†

Abstract

Silver-polyoxometalate (Ag-POM) complexes, safeguarded by polyoxometalate (POM) ligands, are scarcely documented. Nonetheless, the targeted synthesis of Ag-POMs remains a focal point due to their prospective applications. Here, we successfully obtained an {Ag6} cluster, characterized as Na6K6H25[(P2W12O43)2(PW6O18)2(WO5){Ag2(Ag6O19)}(H2O)3]∙93H2O (1), within an annular polyoxometalate framework via a ligand-protecting strategy in a purely inorganic environment. The hexavacant Dawson-type precursor, [H2P2W12O48]12−, served as a structure-directing as well as a functionalizing unit in the process of synthesis. Proton conducting measurements of {Ag6} indicated good proton conductivity performance, achieving a conductivity value (σ) of 3.0×10−2 S cm−1 at 368 K and 98% relative humidity (RH). Furthermore, the {Ag6} clusterdemonstrated significant catalytic activity in the selective photoreduction of nitrobenzene.