Metal-free negative linear compressibility (NLC) material - the cocrystal of 1,2-bis(4-pyridyl)ethane and fumaric acid.

Materials that show significant negative linear compressibility (NLC) reported so far suffer from a number of shortcomings that affect their applicability. The cocrystal of 1,2-bis(4-pyridyl)ethane and fumaric acid, which exhibits exceptional NLC behaviour, overcomes these problems and sets the foundation for the development of environmentally friendly metal-free NLC materials.