Generate gromacs topology for hypothetical structure

Hi everyone,

I am trying to simulate a hypothetical material based on the graphene layers. However, I am facing some issues trying to generate the ITP file for the material. For the graphene layer, several tools work well, if I consider graphene as a bunch of benzene, but if I do some modifications to the layers I face several problems.

Does anyone know some tool that just recognizes the connections between the atoms? I do not want to find a force field, just create the ITP file with the connections between the atoms.

Thank you.