Interestingly, Cu18PTT NCs exhibited a distinct trend in the selectivity of CO2RR products. Although the Cu18PTT NCs showed a modified core geometry compared to Cu11PTT NCs, they still produced HCOOH, with the maximum FEHCOOH reaching ~35% at -1.2 V (vs. RHE). The current density plots for the products formed at a potential of -1.2 V (vs. RHE), further validate the observed trends in product distribution driven by the differing reactivities of these NCs (Figure ). Among these NCs, the Cu11PTT NC exhibits the highest current density for HCOOH production, followed by Cu18PTT and Cu11ABT NCs. So, it can be initially assumed that the superior role of surface ligands over structural architecture in governing CO2RR selectivity of HCOOH. A comparison of the reactivity between Cu11PTT and Cu18PTT NCs highlights the critical role of structural architecture in shaping catalytic activity. Notably, compared to our previous findings with [Cu14(SC2H4Ph)3(PPh3)8H10] + , [Cu14(SC6H11)3(PPh3)8H10] + , and [Cu58H20(SC2H5)36(PPh3)6] 2+ NCs, the Cu₁₁PTT NC demonstrates superior selectivity for FEHCOOH. This observation indicates that alterations in the geometric structure influence the configuration and properties of the active catalytic sites, thereby leading to variations in the FE of the products. However, the significant discrepancy in the CO2RR reactivity and product selectivity observed between the two Cu11 NCs-Cu11PTT and Cu11ABT-despite their identical geometry and number of Cu atoms, underscores the impact of surface ligand modification.