A π‐Conjugated Van der Waals Heterostructure Between Single‐Atom Ni‐Anchored Salphen‐Based Covalent Organic Framework and Polymeric Carbon Nitride for High‐Efficiency Interfacial Charge Separation

Abstract Semiconductor‐based heterostructures have exhibited great promise as a photocatalyst to convert solar energy into sustainable chemical fuels, however, their solar‐to‐fuel efficiency is largely restricted by insufficient interfacial charge separation and limited catalytically active sites. Here the integration of high‐efficiency interfacial charge separation and sufficient single‐atom metal active sites in a 2D van der Waals (vdW) heterostructure between ultrathin polymeric carbon nitride ( p ‐CN) and Ni‐containing Salphen‐based covalent organic framework (Ni‐COF) nanosheets is illustrated. The results reveal a NiN 2 O 2 chemical bonding in NiCOF nanosheets, leading to a highly separated single‐atom Ni sites, which will function as the catalytically active sites to boost solar fuel production, as confirmed by X‐ray absorption spectra and density functional theory calculations. Using ultrafast femtosecond transient adsorption (fs‐TA) spectra, it shows that the vdW p ‐CN/Ni‐COF heterostructure exhibits a faster decay lifetime of the exciton annihilation (τ = 18.3 ps) compared to that of neat p ‐CN (32.6 ps), illustrating an efficiently accelerated electron transfer across the vdW heterointerface from p ‐CN to Ni‐COF, which thus allows more active electrons available to participate in the subsequent reduction reactions. The photocatalytic results offer a chemical fuel generation rate of 2.29 mmol g −1 h −1 for H 2 and 6.2 µmol g −1 h −1 for CO, ≈127 and three times higher than that of neat p ‐CN, respectively. This work provides new insights into the construction of a π‐conjugated vdW heterostructure on promoting interfacial charge separation for high‐efficiency photocatalysis.