Ag and MOFs-derived hollow CoO decorated in the 3D g-CN for creating dual transferring channels of electrons and holes to boost CO photoreduction performance.

The rapid recombination of photoinduced charge carriers and low selectivity are still challenges for the CO photoreduction. Herein, we proposed that ZIF-67-derived CoO hollow polyhedrons (CoHP) were embedded into NaCl-template-assisted synthesized 3D graphitic carbon nitride (NCN), subsequently, loading Ag by photo-deposition as efficient composites (CoHP@NCN@Ag) for CO photoreduction. This integration simultaneously constructs two heterojunctions: p-n junction between CoO and g-CN and metal-semiconductor junction between Ag and g-CN, in which CoO and Ag serve as hole (h) trapping sites and electron (e) sinks, respectively, achieving spatial separation of charge carriers. The donor-acceptor structure design of NCN realize a good photogenerated e-h separation efficiency. The mesoporous structure of hollow CoO facilitate gas-diffusion efficiency, light scattering and harvesting. And the introduction of plasmonic Ag further strengthens the light-harvesting and charge migration. Benefiting from the rational design, the optimized ternary heterostructures exhibit a high CO-CO yield (562 μmol g), which is about 4-fold as high as that of the NCN (151 μmol g). Moreover, the conjectural mechanism was systematically summarized. We hope this study provides a promising strategy for designing efficient g-CN systems for the CO photoreduction.