Precise Control of Fe ³⁺ Incorporation in Poly(heptazine imide) for Modulating Electronic Structure and Enhanced Photocatalytic Selective Oxidation of Benzyl Alcohol

In this study, Fe 3+ ‐modified poly(heptazine imide) (denoted as FeO x /H‐PHI, abbreviated as FePHI for simplicity) was constructed via an impregnation method by introducing Fe 3+ into Na + ‐intercalated PHI (NaPHI). The incorporated Fe 3+ effectively substituted Na + in the PHI framework, forming highly dispersed FeO x clusters. This modification significantly narrowed the material bandgap from 2.67 to 2.53 eV, extending the visible‐light absorption edge beyond 600 nm. Simultaneously, the FeO x clusters acted as efficient electron traps, suppressing the recombination of photogenerated charge carriers. The optimized FePHI‐50 catalyst (with an Fe loading of 4.48 wt.%) exhibited remarkably enhanced visible‐light activity in the selective oxidation of benzyl alcohol. The performance improvement was attributed to the facilitated hole migration and reactant activation mechanism promoted by the Fe sites. Radical trapping experiments further confirmed that photogenerated holes (h + ) served as the primary active species. This work provides new insights into the structure–activity relationships of metal‐doped polymer photocatalysts and offers a theoretical basis for designing efficient solar‐driven organic synthesis systems.