Wearing Gigantic Silver Armor on Transition‐Metal‐Containing Polyoxometalates: Formation of Supertetrahedral Intercluster Compounds

Compared to versatile polyoxometalate (POM)-templated Ag clusters, the construction of closed Ag clusters using transition-metal-containing polyoxometalates (TMCPOMs) as anionic templates has, to our knowledge, never been reported. In this work, we have synthesized three TMCPOM-templated gigantic closed Ag clusters, [{(Co_0.58W_0.42)₃(OH)₃(Ag_0.5O₃)(SiW₉O₃₄)}₄@Ag₁₁₄Br₄(^tBuC≡C)₇₂]·[SiW₁₂O₄₀]₂·10CH₃CN (1), [{(Cu_0.58W_0.42)₃(OH)₃(Ag_0.5O₃)(SiW₉O₃₄)}₄@Ag₁₁₄Br₄(^tBuC≡C)₇₂]·[SiW₁₂O₄₀]₂ (2), and [{(Co_0.58W_0.42)₃(OH)₃(Ag_0.5O₃)(GeW₉O₃₄)}₄@Ag₁₁₄Br₄(^tBuC≡C)₇₂]·[GeW₁₂O₄₀]₂ (3), using a universal one-pot solvothermal synthetic approach. Single-crystal X-ray diffraction analyses demonstrate that the high-nuclearity transition metal-containing (M = Co/Cu) POMs with idealized T_d symmetry are closely covered by gigantic Ag armors, representing the largest TMCPOM-templated closed Ag clusters to date. Moreover, compounds 1-3 can form interesting supertetrahedral intercluster packing structures through Columbic and hydrogen bonding interactions between the cationic TMCPOM-templated gigantic {Ag₁₁₄} clusters and the counter [XW₁₂O₄₀]^4- (X = Si/Ge) anions. Upon light irradiation, all three compounds exhibited decent photocatalytic CO₂ reduction activity, which is dependent on their different electronic structures.