Rational Design of Vis‐to‐NIR Light Driven Photocatalytic System With Bidirectional Transfer of Charge and Energy for Enhanced Hydrogen Evolution

ABSTRACT The rational design of photocatalytic systems capable of utilizing the full solar spectrum while maintaining efficient charge separation remains a persistent challenge in sustainable hydrogen production. Herein, we combine up‐conversion nanoparticles (UCNPs) with near‐infrared absorbing ability and visible‐light driven covalent organic framework (COF) photocatalyst together to construct a hybrid heterostructure for Vis‐to‐NIR light driven hydrogen production. In this system, UCNPs convert NIR light into ultraviolet and visible light for the utilization of TpPa‐1‐COF, while an effective heterojunction formed between UCNPs and TpPa‐1‐COF benefiting the separation of photogenerated charge carriers. As a result, PNGF(15%)@TpPa‐1‐COF composites achieve an exceptional high hydrogen evolution rate of 126.9 mmol g −1 h −1 , which is 28 times enhancement over pristine TpPa‐1‐COF. The contribution of UCNPs in facilitating the separation of charge carriers of TpPa‐1‐COF was confirmed by measurements of femtosecond transient absorption spectroscopy (fs‐TAS) and various characterizations. The results of control experiments demonstrate that energy band matching between COFs and UCNPs is crucial for the formation of the bidirectional transfer of photogenerated electrons and energy within the photocatalytic system. This provides an innovative strategy for developing an efficient photocatalytic heterojunction system to broaden the utilization of solar light and achieve effective separation of photogenerated charge carriers.