Fluorine intercalation in nitrogen-substituted carbon C x N has been investigated at a temperature ranging from room temperature to 300 o C. C 1 6 N and C 1 4 N yielded the fluorinated products with low C/F ratios, C 3 F under fluorine pressures of 1.0x10 5 and 0.5x10 5 Pa at room temperature. The intercalated fluorine decreased with decreasing nitrogen content in the host C x N, in particular at 0.25x10 5 Pa. X-ray powder diffraction data revealed that fluorine-intercalated C x N samples consisted of mixtures of several stages or mixtures with unreacted phase, having lower stages than those prepared from carbon. XPS and IR absorption spectra indicated the formation of semi-ionic C-F bonds. It was found that fluorine intercalation was much easier in C x N than in carbon between 50 o C and 200 o C. XPS and IR absorption spectra showed that C-F bonding varied from semi-ionic to covalent with increasing fluorination temperature from 50 o C to 300 o C. IR absorption spectrum suggested the formation of NF 2 groups at 300 o C.