Molecular Tuning of Pyrene-Based Conjugated Porous Polymers for Enhanced Photocatalytic Hydrogen Production

Conjugated porous polymers (CPPs) have emerged as promising candidates for photocatalytic H₂ production (PHP) in recent years due to their structural diversity, tunable electronic properties, and high specific surface area. Herein, three CPPs are synthesized by the Suzuki coupling reaction for photocatalytic H₂O splitting to produce H₂. Through molecular tuning strategies, the π-conjugation degree of the CPPs is adjusted, significantly impacting the charge separation and transfer efficiency of the photocatalysts as well as their light-harvesting ability. The optimal photocatalyst, namely PyDF, shows a high photocatalytic H₂ evolution rate of 12.8 mmol g^-1 h^-1 with a large number of continuous visible bubbles, which is up to five times higher than its counterparts. Advanced characterization techniques, including photo-irradiated Kelvin probe force microscopy (KPFM) and femtosecond transient absorption (fs-TA) spectroscopy, together with theoretical calculations, reveal that the PyDF with a smaller dihedral angle has much-improved π-conjugation degree, resulting in higher charge separation and transfer efficiency. This work provides a new perspective for the application of CPPs in the PHP and emphasizes the importance of modulation of the π-conjugation degree.