A Metal–Organic Framework of Organic Vertices and Polyoxometalate Linkers as a Solid-State Electrolyte

A new three-dimensional metal–organic framework (MOF) was synthesized by linking ditopic amino functionalized polyoxometalate N (C4H9) 43MnMo6O18 (OCH2) 3CNH22 with 4-connected tetrahedral tetrakis (4-formylphenyl) methane building units through imine condensation. The structure of this MOF, termed MOF-688, was solved by single crystal X-ray diffraction and found to be triply interpenetrated diamond-based dia topology. Tetrabutylammonium cations fill the pores and balance the charge of the anionic framework. They can be exchanged with lithium ions to give high ionic conductivity (3. 4 × 10–4 S cm–1 at 20 °C), a high lithium ion transference number (tLi+ = 0. 87), and low interfacial resistance (353 Ω) against metallic lithium—properties that make it ideally suited as a solid-state electrolyte. Indeed, a prototype lithium metal battery constructed using MOF-688 as the solid electrolyte can be cycled at room temperature with a practical current density of ∼0. 2 C.