“…Beyond the in-plane manipulation of the M–N fragment’s local environment by varying the coordination number of M atoms, the incorporation of axial ligands emerges as an appealing strategy for modifying the electronic structure and catalytic performance of SACs. − For instance, Ma and Tang demonstrated that functionalizing with various axial ligands can profoundly influence the adsorption and reaction characteristics of the active M–N 4 site, thereby significantly impacting its activity . Among different axial ligands, Cl-modified sites have shown particular promise in fine-tuning the activity, especially for CO 2 RR. − In this context, our initial focus is on tuning the metal center in the g-C 3 N 4 to potentially inhibit the HER, which we define as the primary selectivity. Previous research showed that halogen modification of Mn-doped graphitic carbon nitride (g-C 3 N 4 ) strongly inhibits HER. , However, Pt atoms supported on NiFe-layered double hydroxide with various axial ligands (F, Cl, Br, I, and OH) demonstrated high alkaline HER electrocatalytic activity .…”