Intramolecular Charge Transfer and Extended Conjugate Effects in Donor–π–Acceptor‐Type Mesoporous Carbon Nitride for Photocatalytic Hydrogen Evolution

Abstract Inspired by donor–acceptor (D–A) polymers in organic solar cell and the extended conjugation effect, a conceptual design of D–π–A‐type mesoporous carbon nitride with benzene or thiophene as a π‐spacer is proposed as an efficient photocatalyst for hydrogen evolution. The photocatalyst was successfully synthesized by a one‐pot thermopolymerization based on nucleophilic substitution and a Schiff‐base chemical reaction. On the molecular level, the insertion of an in‐plane benzene as a π‐spacer by forming covalent bonds C=N (acceptor) and C−N (donor) interrupts the continuity of tri‐s‐triazine units and maintains the intrinsic π–π conjugated electronic system. Synchronously, the enlarged electron delocalization and the intramolecular charge transfer induced by polarization provide force‐directed migration of electrons, leading to boosted optical absorption capability and enhanced photogenerated carrier separation. With the synergistic effects of the mesoporous structure and excellent optical and electronic properties, a fivefold increase in the H2 evolution rate compared with that of pristine g‐C3N4 was achieved with robust performance. In addition, other simple aromatic heterocyclic compounds (e.g., pyridine, thiophene and furan)‐based D–π–A structures with a higher hydrogen evolution rate (up to sevenfold increase) were also explored to broaden the application for the design of novel photocatalysts.