Constructing monomolecular active centres on polymeric carbon nitride for selective photocatalytic CO2 reduction to CO

Abstract

The oriented design and construction of active centres for photocatalysts at the atomic/molecular level represents one of the crucial scientific challenges, due to the restricted preparation techniques of high difficulty. In this contribution, a simple self-assembly strategy is innovatively developed to anchor the small conjugated 2,2′-bipyridine copper(II) chloride (Cubpy) molecules on polymeric carbon nitride (PCN) nanosheets in a monomolecular dispersed state, thereby constructing monomolecular active centres. The π–π interaction between Cubpy and PCN effectively results in an upward shift in the Fermi level, an increase in the carrier concentration and an improvement in the charge separation efficiency in the fabricated Cubpy/PCN heterojunction compared to the initial PCN. As a result, the Cubpy/PCN heterojunction achieves selective photocatalytic CO₂ reduction to CO. The optimal Cubpy/PCN-5 exhibits a remarkable CO evolution rate of 16.8 μmol g⁻¹ h⁻¹, reaching 5.5-fold that of the initial PCN (3.05 μmol g⁻¹ h⁻¹). This work delivers a simple and practical design concept for engineering atomic-/molecular-level active centres to enhance the overall performance of photocatalysts.