The major challenge remains on disentangle the inductive (through-structure) and electrostatic (through-space) effects. A series of homogenous substituted iron porphyrins have been systematically studied by Savéant and coworkers for CO2 reduction. Installing an electronwithdrawing substituent was found to lower the overpotential by reducing the electron density around the metal center. In contrast, electron-donating substituents were observed to behave the opposite. A linear correlation between log(turnover frequency) and the standard potential was found when the electronic inductive effect of the substituents was taken into account. However, importantly, incorporating charged substituents stabilized key intermediates through electrostatic attraction or repulsion, causing a significant deviation of those catalysts from the linear correlation. Additionally, effects of sterically hindered substituents on the aggregation of catalysts in the immobilized system have to be taken into account. Figure depicts the homogeneous iron porphyrin complexes mentioned in the previous discussion. The presence of electrondonating and electron-withdrawing substituents resulted in well-understood inductive effect whereas the presence of positively and negatively charged substituents on the ligand resulted in through-space electrostatic effects which is rather challenging to disentangle from the inductive effect. Being able to form hydrogen bonding between the ligand and substrate could also help with stabilizing intermediate. Based on the understanding of the homogenous system, Gotz et al., presented a study on the influences of mesityl and thiophene peripheral substituents asserted on surface attachment. Iron porphyrin complexes with thiophenyl substituents created a dense and planar molecular layer on the silver electrode, embedded with facile electron transfer via Ag-S covalent bonds. On the contrary, bulky mesityl substituents caused less dense coverage of the molecular layer and created less stable interactions. It is important to note that the bulky mesityl groups, which were proved to prevent catalyst aggregation and improve catalytic behavior in solution, now exert a negative effect after immobilization. We note that molecular electrostatic effects significantly affect the catalytic activity and selectivity. Meanwhile, implications of the substituents on the ligands for hybridized metal complexes should also be deliberated after immobilization.