Single-Ion Li⁺, Na⁺, and Mg²⁺ Solid Electrolytes Supported by a Mesoporous Anionic Cu–Azolate Metal–Organic Framework

A novel Cu­(II)–azolate metal–organic framework (MOF) with tubular pores undergoes a reversible single crystal to single crystal transition between neutral and anionic phases upon reaction with stoichiometric amounts of halide or pseudohalide salts. The stoichiometric transformation between the two phases allows loading of record amounts of charge-balancing Li+, Na+, and Mg2+ ions for MOFs. Whereas the halide/pseudohalide anions are bound to the metal centers and thus stationary, the cations move freely within the one-dimensional pores, giving rise to single-ion solid electrolytes. The respective Li+-, Na+-, and Mg2+-loaded materials exhibit high ionic conductivity values of 4.4 × 10–5, 1.8 × 10–5, and 8.8 × 10–7 S/cm. With addition of LiBF4, the Li+ conductivity improves to 4.8 × 10–4 S/cm. These are the highest values yet observed for MOF solid electrolytes.一种具有管状孔道的新型铜(II)-唑基金属有机框架（metal–organic framework, MOF），在与化学计量比的卤化物或类卤化物盐反应时，可在中性相与阴离子相之间发生可逆单晶到单晶转变。两相之间的化学计量比转化可实现MOF材料中负载量创纪录的电荷平衡Li+、Na+及Mg²+离子。卤化物/类卤化物阴离子结合于金属中心，因此固定不动，而阳离子可在一维孔道内自由移动，从而形成单离子固体电解质。分别负载Li+、Na+和Mg²+的材料展现出4.4×10⁻⁵、1.8×10⁻⁵及8.8×10⁻⁷ S/cm的高离子电导率。添加四氟硼酸锂（LiBF₄）后，Li+电导率提升至4.8×10⁻⁴ S/cm。上述数值均为目前已报道的MOF基固体电解质中的最高值。