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, [{(Co0.58W0.42)3(OH)3(Ag0.5O3)(SiW9O34)}4@Ag114Br4(tBuC≡C)72]·[SiW12O40]2·10CH3CN (1), [{(Cu0.58W0.42)3(OH)3(Ag0.5O3)(SiW9O34)}4@Ag114Br4(tBuC≡C)72]·[SiW12O40]2 (2), and [{(Co0.58W0.42)3(OH)3(Ag0.5O3)(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 Td 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.