Self-assembly of polyoxometalate-based metal-organic framework with trefoil sign structural feature as efficient anode for lithium ion batteries

To extend the practical applications of polyoxometalates (POMs) based metal–organic frameworks (POMOFs) in the most cut-ting-edge (lithium ion batteries) LIBs, a new crystalline POMOFs, [Ag₆(H₂trz)₆]·[H₄SiW₁₂O₄₀]·6H₂O (SiW₁₂-Ag-trz), was successfully synthesized and well characterized in the work. Crystal analysis reveals that Keggin-typed POMs [H₄SiW₁₂O₄₀] (SiW₁₂) are inserted into the Ag-trz helical chain to construct 3D POMOFs with open pore channels with trefoil sign structural feature, in which SiW₁₂ polyoxoanion exhibiting the most diverse coordination modes in the reported crystalline POMOFs, to the best our knowledge. Because the pore channels facilitate the storage and release of lithium ions, and the SiW₁₂ polyoxoanion growing on the framework serves as an excellent electron sponge, crystalline SiW₁₂-Ag-trz as an anode material for lithium-ion batteries (LIBs) exhibits highly reversible capacity and rate capability. Moreover, to illustrate the lithium storage, the impedance spectra and cyclic voltammetry (CV) with different scan rates during the first and 50th charge process were studied in details.