Inhibiting the generation of oxidizing free radicals by enhancing intramolecular electron complementary effect in large-conjugated carbon nitride for stable NIR H2 production

Photocatalytic processes in solution systems tend to induce secondary reactions. Particularly, the generation of oxidizing free radicals can impede the efficient progression of the target main reactions and compromise the stability of photocatalysts. Herein, a large-conjugated carbon nitride (OQCN) with a reinforced intramolecular electron interaction effect is fabricated to enable long-term stable photocatalytic reactions. The large-conjugated structure constructed by quinoline and heptazine significantly broadens the light response range of OQCN to the near-infrared region. Furthermore, the appropriate electron-withdrawing capacities of quinoline and heptazine not only facilitate the formation of a donor-acceptor (D-A) structure for ordered electron transfer, but also trigger an electron complementation process in OQCN upon photoexcitation. Through the rapid electron rearrangement between quinoline and heptazine moieties, excessive oxidation processes are suppressed, and the production of hydroxyl radicals is substantially inhibited. Consequently, OQCN exhibits considerable hydrogen evolution activity under near-infrared irradiation, with no apparent degradation in photocatalytic performance during prolonged reaction. Moreover, its oxygen-phobic property and superoxide radical-inhibiting effect endow OQCN with excellent resistance to long-term soaking treatment. This work uncovers an effective electron modulation mechanism for enhancing the stability of organic photocatalysts. • A one-step method modulates the morphology and conjugated framework of g-C 3 N 4 . • The large conjugated structure realizes the NIR response of picked g-C 3 N 4 (OQCN). • Modulation of morphology and chemical structure optimizes the dynamics of carriers. • The electron complementary effect is revealed to enhance the stability of OQCN.