Characterization of a Carbon−Nitrogen Network Solid with NMR and High Field EPR

Considerable attention has been focused on developing a synthetic route to a carbon−nitrogen material with mechanical and thermal properties comparable or superior to those of diamond. To date, no substance with the desired C<INF>3</INF>N<INF>4</INF> stoichiometry in a silicon-nitride crystal lattice has been reported. One of the principal difficulties in the pursuit of ultrahard carbon−nitrogen (CN) solids is the characterization of amorphous CN samples. We describe a solid-state NMR study of a paracyanogen-like solid utilizing ¹³C-¹⁵N adiabatic-passage Hartmann−Hahn cross-polarization (APHH-CP) to perform dipolar filtering and show that this method is well-suited for recoupling ¹³C-¹⁵N in network solids. In addition, high-frequency electron paramagnetic resonance (EPR) indicates a density of electron spins of approximately 1 × 10¹⁷ e^-/cm³. We conclude by discussing how NMR and EPR data may be useful for optimizing CN-polymer samples as potential precursors for ultrahard carbon nitrogen solids.