Hollow sp2-conjugated covalent organic framework encapsulating thiophene-based photosensitizer for enhanced visible-light-driven hydrogen evolution

Vinylene-linked covalent organic frameworks (COFs) have gained increasing attention for photocatalytic hydrogen evolution. However, the photocatalytic activity of vinylene-linked COFs has been restricted due to low exciton dissociation efficiency and wide band gap. Herein, we fabricated a novel p-n type Z-scheme heterostructure, g2T-T@HCOFs, through the hybridization of vinylene-linked COFs with a hollow structure and thiophene-based photosensitizer (g2T-T) using a template method and post-encapsulating modification. The hollow-structured HCOFs enable uniform encapsulation of the g2T-T both within their channels and on their surfaces, which facilitates the formation of a firm and stable interface between n-type HCOF and p-type g2T-T. Therefore, the encapsulation of g2T-T enables the realization of a Z-scheme pathway for efficient charge separation and transfer, leading to enhanced electron accumulation within the HCOFs during water splitting. Consequently, the obtained p-n type Z-scheme heterostructure g2T-T@HCOFs exhibit a remarkable 5.5-fold enhancement in visi-ble-light-induced hydrogen evolution activity compared to the pristine COF.