Atomically Precise Silver Clusters Stabilized by Lacunary Polyoxometalates with Photocatalytic CO 2 Reduction Activity.

The syntheses of atomically precise silver (Ag) clusters stabilized by multidentate lacunary polyoxometalate (POM) ligands have been emerging as a promising but challenging research direction, the combination of redox-active POM ligands and silver clusters will render them unexpected geometric structures and catalytic properties. Herein, we report the successful construction of two structurally-new lacunary POM-stabilized Ag clusters, TBA 6 H 14 Ag 14 (DPPB) 4 (CH 3 CN) 9 [Ag 24 (Si 2 W 18 O 66 ) 3 ] ⋅ 10CH 3 CN ⋅ 9H 2 O ({Ag 24 (Si 2 W 18 O 66 ) 3 }, TBA=tetra-n-butylammonium, DPPB=1,4-Bis(diphenylphosphino)butane) and TBA 14 H 6 Ag 9 Na 2 (H 2 O) 9 [Ag 27 (Si 2 W 18 O 66 ) 3 ] ⋅ 8CH 3 CN ⋅ 10H 2 O ({Ag 27 (Si 2 W 18 O 66 ) 3 }), using a facile one-pot solvothermal approach. Under otherwise identical synthetic conditions, the molecular structures of two POM-stabilized Ag clusters could be readily tuned by the addition of different organic ligands. In both compounds, the central trefoil-propeller-shaped {Ag 24 } 14+ and {Ag 27 } 17+ clusters bearing 10 delocalized valence electrons are stabilized by three C-shaped {Si 2 W 18 O 66 } units. The femtosecond/nanosecond transient absorption spectroscopy revealed the rapid charge transfer between {Ag 24 } 14+ core and {Si 2 W 18 O 66 } ligands. Both compounds have been pioneeringly investigated as catalysts for photocatalytic CO 2 reduction to HCOOH with a high selectivity.