“…The intensity peak of C 4 around 165.21 ppm in C 3 N 4 , associated with the S atom substitution position, was signicantly higher than that of C 2 (156.98 ppm), aligning with the XPS conclusion, suggesting that the substitution of non-metallic elements in the matrix involved C atoms rather than N atoms. Moreover, to thoroughly investigate the substitution sites of non-metallic elements, 31 P NMR investigation was undertaken utilizing the active units of Cu-C 3 N 4 -P (Fig. S12 †), revealing solely distinctive peaks corresponding to P-N. 52 Based on this inference, in the Cu-C 3 N 4 -HA, non-metallic elements substitute for C in the matrix, forming X-N coordination.…”