Polyoxometalate-templated assembly of homo- and heterometallic silver clusters

In this work, we have synthesized and characterized three heterometallic [Ni₄(OH)₃(NO₃)₃(SiW₉O₃₄)@Ag₃₉(^tBuC≡C)₂₄(NO₃)₆](NO₃) (Ag₃₉Ni₄), [Co₄(OH)₃(NO₃)₃(SiW₉O₃₄)@Ag₃₉(^tBuC≡C)₂₄(NO₃)₆](NO₃) (Ag₃₉Co₄) and [Cu₃(OH)₂O(SiW₉O₃₄)@Ag₄₂(^tBuC≡C)₂₇(NO₃)₃Cl](NO₃)₃·CH₃CN (Ag₄₂Cu₃) clusters and one homometallic [(SiW₉O₃₄)@Ag₄₄(^tBuC≡C)₂₆Cl₈]·CH₃CN (Ag₄₄) cluster using lacunary polyoxometalates (POMs) as anionic templates under facile solvothermal conditions. Structural analyses reveal their similar core-shell architectures featuring a POM anionic template and a bowl-shaped silver shell stabilized by surface organic alkynyl (^tBuC≡C⁻) ligands. Various physicochemical and catalytic studies have characterized their temperature-dependent photoluminescence, photothermal conversion performance, and catalytic activity. Particularly, the enhanced catalytic performance towards 4-nitrophenol reduction is observed in the heterometallic cluster-catalyzed systems, where Ag₃₉Ni₄, Ag₃₉Co₄, and Ag₄₂Cu₃ exhibit higher catalytic activity than Ag₄₄. Such remarkable catalytic enhancement reveals that incorporating heterometal atoms into Ag clusters will be a feasible strategy to adjust the catalytic performance of POMs-templated Ag clusters.