Insight into self‐dissociation of poly(heptazine imide) nanosheets enables boosted CO2 photoreduction

Doping triazine units over poly(heptazine imide) (PHI) nanosheets outperforms higher CO2 reduction efficiency than the individual counterparts. Herein, we report a molten salt‐steam thermal‐assisted approach of coupling KCl and Mg(OH)2 for designing highly efficient triazine‐doped PHI (TPHI) in which the n‐type dopant of the triazine unit is produced from the self‐dissociation of the heptazine. The developed TPHI demonstrates the fine‐tuned hydrophilicity, enhanced electron transportation, and promoted reductive ability, evidenced by contact angle, photoelectrochemical, femtosecond transient absorption, surface photovoltage tests, energy band evaluation, and corresponding calculations. The optimized TPHI sample facilitates CO generation (25.1 μmol h−1 g−1) through the photocatalytic CO2 reduction reaction under solar‐simulated light irradiation. Our insight enables a simple strategy for molecular‐level electron manipulations in highly effective polymeric photocatalysts using n‐dopant self‐doping engineering.