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

Conjugated porous polymers (CPPs) have emerged as promising candidates for photocatalytic H 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 HO splitting to produce H. 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 H evolution rate of 12.8 mmol g h 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.