Building Asymmetric Zn-N Bridge between 2D Photocatalyst and Co-catalyst for Directed Charge Transfer toward Efficient HO Synthesis.

Two-dimensional (2D) polymeric semiconductors are a class of promising photocatalysts; however, it remains challenging to facilitate their interlayer charge transfer for suppressed in-plane charge recombination and thus improved quantum efficiency. Although some strategies, such as π-π stacking and van der Waals interaction, have been developed so far, directed interlayer charge transfer still cannot be achieved. Herein, we report a strategy of forming asymmetric Zn-N units that can bridge nitrogen (N)-doped carbon layers with polymeric carbon nitride nanosheets (CN-Zn-N(C)) to address this challenge. The symmetry-breaking Zn-N moiety, which has an asymmetric local charge distribution, enables directed interfacial charge transfer between the CN photocatalyst and the N-doped carbon co-catalyst. As evidenced by femtosecond transient absorption spectroscopy, charge separation can be significantly enhanced by the interfacial asymmetric Zn-N bonding bridges. As a result, the designed CN-Zn-N(C) catalyst exhibits dramatically enhanced HO photosynthesis activity, outperforming most of the reported CN-based catalysts. This work highlights the importance of tailoring interfacial chemical bonding channels in polymeric photocatalysts at the molecular level to achieve effective spatial charge separation.