In this communication, we present a strategy to fine-tune the electronic structure of gold atoms by means of post-synthetic modification of IRMOF-3 (iso-reticular metal organic framework-3) with salicylaldehyde derivatives. Changes in the electronic structure of gold were predicted by theoretical calculations and determined by resonant inelastic X-ray scattering (RIXS) at the gold L₃ edge. Modification of the coordinating group affected the relative HOMO and LUMO energy levels, resulting in a change of the HOMO–LUMO gap. The ability to fine tune electronic structure may lead to tailoring of the catalytic performance and material electronics states.