Ni Single Atoms and Prussian Blue Analogs Comodified Poly(heptazine imide) for Efficient CO ₂ Photoreduction

Poly(heptazine imide) (PHI) has garnered significant attention as a promising material for photocatalytic CO2 reduction. However, its practical application is hindered by limitations stemming from inefficient electron-mediated reduction processes and sluggish hole-driven oxidation kinetics. Herein, the Ni single atoms and hollow CoFe Prussian blue analogs were precisely decorated on PHI (CoFePBA@Ni-PHI) through a two-step calcination and in situ ion exchange-growth conversion process. The optimized CoFePBA@Ni-PHI photocatalyst demonstrates a superior CO evolution rate of 41.3 μmol g–1 h–1 in pure water without sacrificial agents, representing a 4.5-fold and 5.7-fold enhancement compared to pristine PHI and g-C3N4, respectively. The enhanced photocatalytic performance is primarily ascribed to the synergistic redox dual-site modification, where Ni single atoms serve as electron extractors to promote CO2 reduction, while hollow CoFePBA functions as hole-trapping sites to facilitate water oxidation, thereby collectively accelerating the overall photocatalytic process. This work elucidates the critical role of dual redox site engineering in photocatalytic systems and provides a rational design strategy for constructing efficient photocatalysts toward solar-driven fuel production.