Intramolecular Quaternary Carbon Nitride Homojunction for Enhanced Visible Light Hydrogen Production

Abstract In this work, an intramolecular carbon nitride (CN)‐based quaternary homojunction functionalized with pyridine rings is prepared via an in situ alkali‐assisted copolymerization strategy of bulk CN and 2‐aminopyridine for efficient visible light hydrogen generation. In the obtained structure, triazine‐based CN (TCN), heptazine‐based CN (HCN), pyridine unit incorporated TCN, and pyridine ring inserted HCN constitute a special multicomponent system and form a built‐in electric field between the crystalline semiconductors by the arrangement of energy band levels. The electron‐withdrawing function of the conjugated heterocycle can trigger the skeleton delocalization and edge induction effect. Highly accelerated photoelectron‐hole transfer rates via multi‐stepwise charge migration pathways are achieved by the synergistic effect of the functional group modification and molecular quaternary homojunction. Under the addition of 5 mg 2‐aminopyridine, the resulting homojunction framework exhibits a significantly improved hydrogen evolution rate of 6.64 mmol g −1 h −1 with an apparent quantum efficiency of 12.27% at 420 nm. Further, the catalyst verifies its potential commercial value since it can produce hydrogen from various real water environments. This study provides a reliable way for the rational design and fabrication of intramolecular multi‐homojunction to obtain high‐efficient photocatalytic reactions.