Carbon nitrides are emerging as an important class of materials with applications that range from Li+ ion and electronic charge storage in batteries and supercapacitors, visible-UV light harvesting for photocatalysis and photovoltaics, to fuel cell and electrolyser catalyst supports. The focus of this study are the polytriazine imide (PTI) materials, which are the only crystalline graphitic carbon nitrides that can be synthesised readily and reproducibly from molten LiCL. Despite the interest in these materials, the structure is unknown, especially the location of H and Li. Furhtermore, a recent observation has been that the Li and Cl can be removed from the PTI materials by washing with water. This can influence properties such as water-splitting. The goal of this study is to locate guest atoms (Li and H, which cannot be seen by X-rays) in these carbon nitrides using neutron scattering.