A Metal-Organic Framework with Tetrahedral Aluminate Sites as a Single-Ion Li⁺ Solid Electrolyte

We demonstrate the synthesis of the first anionic aluminum metal-organic framework (MOFs) constructed from tetrahedral AlO₄ sites. Al-Td-MOF-1 was obtained in a simple two-step synthesis by condensation of 1,4-dihydroxybenzene and lithium aluminum hydride into an amorphous aluminate framework before applying a solvothermal treatment under basic conditions to obtain the crystalline Al-Td-MOF-1 with a chemical composition of Li[Al(C₆ H₄ O₂ )₂ ]. The overall Al-Td-MOF-1 structure consists of one-dimensional chains of alternating edge-sharing AlO₄ and LiO₄ tetrahedral sites describing unidirectional pore channels with a square window aperture of ≈5×5 Ų , best described topologically as a uninodal 6-coordinated snp rod net. Al-Td-MOF-1 features the highest Li⁺ loading reported to date for a MOF (2.50 wt %) and proved to be an effective single-ion solid electrolyte. An ionic conductivity of 5.7×10^-5  S cm^-1 was measured for Al-Td-MOF-1 and the beneficial contribution of crystallinity was evidenced by an 8-fold increase in conductivity between the disordered and crystalline material.