  Based on first principles calculations, we predicate that Bi on a graphene
derivate, $g$-C$_{14}$N$_3$, which involves a $3\times 3$ unit cell of graphene
with four C atoms substituted by three N atoms, is a topological insulator with
a gap of 50~meV. With the help of maximally localized Wannier functions, we
find that the band inversion gap can be determined by examining a pair of
interaction parameters between the two involved bands. Accordingly, a phase
diagram for band inversion of topological materials as a function of the
interactions is obtained. The conclusion also holds for Sb, Ir and Rh on
$g$-C$_{14}$N$_3$. These materials are topological nontrivial either insulator
or semimetal, indicating that $g$-C$_{14}$N$_3$ is a good platform for
conceiving topological materials.
