However, the intensity of N K-edge

However, the intensity of N K-edge declines in CN–B as com￾pared with that of pristine g-C3N4, the electron back-donation
from B to N site could be then expected in CN–B, in consid￾eration of the lower electronegativity of boron than carbon and
nitrogen. For CN–H, the intensity of N K-edge is lower than
that of g-C3N4, which could be explained by the nitrogen defects
introduced in CN–H.[24] Particularly, the peak intensity ratio of
N1/N2 (≈1.3, Table S4, Supporting Information) in CN–H is
larger than that in g-C3N4 (≈1.2, Table S4, Supporting Informa￾tion), revealing that there are more defects at N2 sites in CN–H,
mainly because the length of N2–C bridge bond is longer than
that of N1–C, N2–C has lower covalent intensity than N1–C,
and thus N2–C breaks more easily than N1–C.[24] For BH400,
it is obviously observed that both N1 peak and N2 peak are less
intense as compared with CN–B or CN–H, meaning that both
the electron back-donation effect and the nitrogen de