Site‐Programmable Molecular Engineering of Donor‐π‐Acceptor g‐C ₃ N ₄ for High‐Efficiency CO ₂ Photoreduction

Abstract Modulation of molecular dipole and π‐electron delocalization is currently a central strategy for designing efficient g‐C 3 N 4 ‐based photocatalysts for CO 2 reduction. Herein, a site‐programmable molecular engineering is reported by integrating the ortho/meta/para‐aminobenzonitrile into g‐C 3 N 4 to construct a donor‐π‐acceptor (D‐π‐A) structure and synergistically regulate dipole alignment and charge distribution. Among these engineered g‐C 3 N 4 , the para‐substituted system exhibits a strong intramolecular dipole field and an extended π‐conjugation, achieving CO and CH 4 production rates of 138.3 and 23.2 µmol g −1 h −1 , which represents one of the highest photocatalytic performances reported to date among g‐C 3 N 4 ‐based photocatalysts with D–A structures. Density functional theory calculations reveal that the D‐π‐A configuration synchronously facilitates interfacial CO 2 adsorption, redistributes surface charge density, and lowers the activation energy barrier. This work establishes a site‐programmable platform for dipole‐guided molecular engineering, offering mechanistic insights into charge dynamics in D‐π‐A photocatalysts.