  Metal-Organic Frameworks (MOFs) have gained much interest due to their
intrinsic tunable nature. In this work, we study how linker functionalization
modifies the electronic structure of the host MOF, more specifically the
MIL-47(V)-R (R=-F, -Cl, -Br, -OH, -CH$_3$, -CF$_3$, and -OCH$_3$). It is shown
that the presence of a functional group leads to a splitting of the
$\pi$-orbital on the linker. Moreover, the upward shift of the split-off
$\pi$-band correlates well with the electron withdrawing/donating nature of the
functional groups. For halide functional groups the presence of lone-pair back
donation is corroborated by calculated Hirshfeld-I charges. In case of the
ferromagnetic configuration of the host MIL-47(V$^{\mathrm{+IV}}$) material a
half-metal to insulator transition is noted for the -Br, -OCH$_3$, and -OH
functional groups, while for the anti-ferromagnetic configuration only the
hydroxy-group results in an effective reduction of the band gap.
