Bifunctional CdS/COF S-scheme photocatalyst for enhanced H2 evolution and organic synthesis

It is an efficient strategy to construct photocatalysts by integrating the advantages of inorganic semiconductors and covalent organic frameworks (COFs) for H2 generation along with simultaneous organic oxidation. Herein, an inorganic/organic CdS/COF (denoted as TpBD) 2D heterostructure is fabricated by an electrostatic self-assembly method. The ultrathin 2D structure can reduce charge transfer distance, enhance light absorption, and multiply reaction sites while the S-scheme heterojunction improves the charge separation efficiency. The CdS/COF composite acquires an outstanding photocatalytic activity of 15.1 mmol/g/h, and can simultaneously convert cheap ascorbic acid to value-added 2,3-diketo-L-gulonic acid. The Hall effect test elucidates the dynamics of carrier migration. The electron paramagnetic resonance analysis, photo-irradiated Kelvin probe force microscopy, femtosecond transient absorption spectroscopy, theoretical calculation, and in-situ irradiation X-ray photoelectron spectroscopy measurements confirm the superiority of S-scheme heterojunction for charge carrier transfer. This research presents new inspiration to develop efficient photocatalysts for hydrogen production and green chemical production.