To gain further insight into the local structure of the catalyst and to investigate any potential structural changes upon material doping with Cu 2+ ions, solid-state magic angle spinning nuclear magnetic resonance (MAS NMR) was performed. The solid-state MAS NMR spectra of all NMRactive nuclei present in the material ( 1 H, 13 C, 15 N, and 19 F) are shown in Figure . The 1 H MAS NMR spectrum (Figure ) of Cu@f-gC3N4 showed two dominant signals at 8.6 ppm and 3.9 ppm from -NH linkers and -NH2 terminal groups, respectively. The high intensity of the signal from -NH linkers compared to that of -NH2 terminal groups indicated a high degree of polymerization. Figure depicted two 13 C signals corresponding to the "edge" (Ce; 165 ppm) and the "internal" (Ci; 157 ppm) carbon sites, in accordance with the material structure. The higher intensity of the Ce signal than the Ci signal was expected since the distance between Ce and protons of the -NH and -NH2 groups was shorter, allowing for more efficient cross-polarization in the CPMAS experiment. In the 1 H-15 N CPMAS spectrum (Figure ), nitrogen resonances from all four different types of nitrogen environments present in the material were observed. The signal at -187 ppm and -223 ppm originated from the nitrogen atoms situated at the edge (Ne) and inside (Ni) of the monomer units, respectively. The number of Ne sites in relation to Ni was expected to be 6:1, but the signal integral at -187 ppm when compared -223 ppm was even higher than the factor of 6, since the distance of the Ni-type nitrogen atoms to the closest protons was substantially longer than in the case of Ne sites, which is in accordance to the material structure and corroborates signal assignment. The other two signals at -244 ppm and -265 ppm corresponded to -NH linkers and -NH2 terminal groups, respectively. Note that the signal of the latter group is overrepresented in the spectrum due to more efficient cross-polarization from the two protons involved. Considering that the 1 H MAS, 13 C CPMAS, and 15 N CPMAS spectra were comparable to the recently reported NMR study on the related polymeric carbon nitride , it can be concluded that doping with Cu 2+ ions did not significantly affect the overall structure and polymerization degree of the materials to any significant extent. However, in the 19 F MAS NMR spectrum shown in Figure , a new signal appeared at -202 ppm in addition to the resonance signal at -105 ppm that was previously observed for the undoped polymeric carbon nitride. The 19 F chemical shift of -105 ppm indicated the presence of the =CF2 moiety and consequently confirmed the successful incorporation of the fluorine atoms at one specific chemical site. To determine if the appearance of the signal at -202 ppm was due to the introduction of Cu 2+ ions in the material, an additional 19 F MAS spectrum was recorded using a shorter relaxation delay (0.2 s, Figure red trace). The spectrum showed that even using a shorter relaxation delay of 0.2 s, the intensity of the signal at -202 ppm was almost not affected, while the signal at -105 ppm was completely saturated and not observed in the spectrum under such detection conditions. This can be explained by paramagnetic relaxation enhancement for 19 F nuclei in close contact with paramagnetic Cu 2+ ions. The additional signal with a shift of -202 ppm may have originated from an induced paramagnetic NMR shift due to unpaired electron(s) of the Cu 2+ ions .