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

## TL;DR

This paper explores the unique properties of 2D frameworks made from lithium ions and dinitriles, showing they have low melting points and unusual thermal expansion.

## Contribution

The study introduces new 2D frameworks with unique mechanical and thermal properties due to weak Li+-dinitrile interactions.

## Key findings

- The frameworks exhibit low melting temperatures below 100 °C.
- They show large positive and negative thermal expansion.
- Metal ion diffusion was observed in the 2D structures.

## Abstract

We constructed two-dimensional (2D) molecular frameworks composed of lithium ions (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 features were uniquely observed in the integration of Li+ and dinitriles into extended molecular structures.

We synthesised four crystalline frameworks from lithium ions and aliphatic dinitrile molecules. Properties based on the weak metal–ligand interactions were studied based on the understanding of well-defined crystal structures.