Donor-acceptor engineering with defect-modulating in covalent organic frameworks for enhanced photocatalytic hydrogen evolution

Covalent organic frameworks (COFs) have emerged as promising photocatalysts for hydrogen production due to their unique optical absorption properties, tunable electronic structures, high porosity, and large specific surface areas. However, practical applications of conventional COFs are limited by critical limitations, including rapid photogenerated carrier recombination and reliance on noble metal co-catalysts. In this study, we propose an innovative defect-control strategy: using 3,5-dimethylbenzaldehyde (DMBA) as a modulator to precisely regulate defect density in TpPa-1-COF materials, which significantly enhances the photocatalytic hydrogen production performance. Notably, the noble-metal-free 7% D-TpPa-1 sample with a tailored defect structure exhibits exceptional catalytic activity, achieving a hydrogen production rate of 1.71 mmol g −1  h −1 (32-fold higher than pristine TpPa-1 at 0.053 mmol g −1  h −1 ), and maintaining excellent cycling stability. Additionally, the photocatalyst demonstrates a maximum apparent quantum efficiency of 5.38% under 420 nm light illumination at 40 °C. Theoretical analysis reveals that the defects acting as electron-donating groups effectively promote the separation of photogenerated charges, while a shift of the conduction band potential to more negative values significantly enhances the reducing performance. This work provides a novel strategy for designing high-performance noble-metal-free COF photocatalysts, as well as a new way for efficient solar-to-hydrogen energy conversion.