Beyond Second Coordination Shell: Long‐Range π‐Electrons Delocalization Engineering in Single‐Atom Catalysts for CO ₂ Electroreduction

Although long-range charge delocalization beyond the second coordination shell critically influence the geometric and electronic properties of single-atom active sites, their systematic modulation to enhance multielectron catalytic processes remains largely unexplored. Here, we demonstrate a site-specific strategy to engineer the nickel tetraphenylporphyrin (NiTPP) precursors by selectively cleaving carbon-carbon single bonds at the β-carbon sites. This approach preserves the Ni-centered first and second coordination shells while systematically removing peripheral π-electron delocalization in extended coordination environments. The resultant Ni-N₄ catalyst exhibits a 29-fold enhancement in CO faradaic efficiency at -1.4 V versus RHE compared to original counterparts. Notably, it maintains 98.3% CO selectivity at industrial-grade current densities up to 500 mA cm^-2 in flow cell. Combined experimental and theoretical analyses reveal that the electron-enriched Ni sites, arising from precisely regulated charge delocalization in higher coordination shells, facilitate stabilization of the critical *COOH intermediate. Our findings establish a paradigm for advanced catalyst design through deliberate engineering of higher coordination shells.