Super Mg2+Conductivity around 10-3 S cm-1 Observed in a PorousMetal-Organic Framework

Wefirst report a solid-state crystallineMg2+conductorshowing a superionic conductivity of around 10-3Scm-1at ambienttemperature, which was obtained using the pores of a metal-organicframework (MOF), MIL-101, as ion-conducting pathways. The MOF, MIL-101 superset of{Mg(TFSI)2}1.6(TFSI-= bis(trifluoromethanesulfonyl)imide), con-taining Mg2+inside its pores, showed a superionic conductivity of 1.9x10-3Scm-1at room temperature (RT) (25 degrees C) under the optimal guest vapor(MeCN), which is the highest value among all Mg2+-containing crystallinecompounds. The Mg2+conductivity in the MOF was estimated to be 0.8x10-3Scm-1at RT, by determining the transport number of Mg2+(tMg2+=0.41), which is the level as high as practical use for secondary battery.Measurements of adsorption isotherms, pressure dependence of ionic conductivity, and in situ Fourier transform infraredmeasurements revealed that thesuper Mg2+conductivityis caused by the efficient migration of the Mg2+carrier with the help ofadsorbed guest molecules.

Automated summary

We report the first solid-state crystalline Mg2+ conductor utilizing the pores of a metal-organic framework (MOF) as ion-conducting pathways, achieving superionic conductivity. The Mg2+ conductor exhibits a conductivity of 10-3Scm-1 at room temperature, which is the highest among all Mg2+-containing crystalline compounds. The efficient migration of the Mg2+ carrier is facilitated by the adsorbed guest molecules.