Polycyclic nitrogen network?
I searched CCDC for the infinite structures with the following building block:



where where each vertex contains any non-metal atom linked by any type of bond. The only known crystal structure that would meet these criteria is $\ce{[B12]2[CBC][C2]Mg_{1.42}}$ where $\ce{B12}$ icosahedra are linked via $\ce{B–C}$ and $\ce{B–B}$ bonds forming the moieties of the previously shown topology:


  
  Figure 2. Projection of the $\ce{B25C4Mg_{1.42}}$ structure onto the $0ac$ plane (the block of icosahedra of boron carbide structure is marked by shading).


Unfortunately, no similar structures are found for nitrogen yet. Also, the structural motif breaks on boron clusters, but this is the closest as I was able to get.

Reference


Ponomarev, V. I.; Konovalikhin, S. V.; Kovalev, I. D.; Vershinnikov, V. I.; Borovinskaya, I. P. Mendeleev Communications 2014, 24 (1), 15–16. DOI: 10.1016/j.mencom.2013.12.004.