Soft crystalline properties of 2D frameworks constructed from lithium ion and dinitriles

Abstract

We constructed two-dimensional (2D) molecular frameworks composed of lithium ion (Li⁺) and dinitrile aliphatic ligands to explore their mechanical and thermal properties. Calorimetry, X-ray diffraction, density functional theory calculations, alternating current impedance, and solid-state nuclear magnetic resonance evidenced behaviours and properties originating from the weakly-linked 2D system. We found low melting temperatures (< 100 °C), high mechanical deformability, large positive and negative thermal expansion, and metal ion diffusion. These were uniquely observed in the integration of Li⁺ and dinitriles into the extended molecular structures.