Efficient Photocatalytic Hydrogen Evolution by Modulating Excitonic Effects in Ni-Intercalated Covalent Organic Frameworks

Covalent organic frameworks (COFs) as appealing platforms have received tremendous interest in the field of photocatalytic H-2 evolution owing to their well-defined structures and tailor-made function. However, excitonic effects resulting from Coulomb interactions between electron-hole pairs are key rate-determining processes in photocatalytic hydrogen evolution, which are usually ignored. Thus, it is of profound significance and highly desired, but it is still a challenge, to explore new routes to modulate excitonic dissociation in COFs for boosting photocatalysis. To address this challenge, Ni-intercalated fluorenone-based COFs (Ni-COF-SCAU-1) at the imine linkage, are proposed for the first time, and demonstrated to exhibit the enhanced polarization electric field; thus, facilitating the Hall electron mobility and the dissociation of singlet excitons into free charge carriers under photoexcitation to participate in the surface hydrogen evolution reaction. Benefiting from these results, Ni-COF-SCAU-1 displays a hydrogen production rate of 197.46 mmol center dot g(-1) h(-1) under visible light irradiation with an apparent quantum efficiency (AQE) up to 43.2% at 420 nm. This work offers an in-depth understanding of the crucial role of the interlayer atomic interface in improving photocatalytic hydrogen evolution and paves a new way for excitonic regulation in the COFs.

Automated summary

Covalent organic frameworks (COFs) have attracted significant interest in the field of photocatalytic hydrogen evolution due to their well-defined structures and tailor-made function. However, the excitonic effects resulting from Coulomb interactions are often overlooked, which are crucial for the rate-determining processes. Therefore, it is important and challenging to explore new routes for modulating excitonic dissociation in COFs for enhancing photocatalysis.