Covalent Triazine Frameworks Decorated with Pyridine-Type Carbonitride Moieties: Enhanced Photocatalytic Hydrogen Evolution by Improved Charge Separation

A simple procedure of calcination under an Ar atmosphere has been successfully applied to create a covalent triazine framework bearing pyridine-type carbonitride moieties (PCN@CTF). The appending of PCN on the CTF led to visible light absorption at up to 600 nm in the UV/Vis diffuse-reflectance spectra. Photoluminescence and electrochemical impedance spectroscopy have been applied to clarify how modification of the CTF with PCN enhanced the separation efficiency of photoexcited charge carriers. An optimized 1%PCN@CTF sample showed the highest photocatalytic hydrogen evolution reaction (HER) rate of 170.2 +/- 2.3 mu mol g(-1).h(-1), 3.9 times faster than that over the pristine CTF. The apparent quantum efficiency of the HER peaked at (7.57 +/- 0.10)% at 490 nm. This representative 1% PCN@CTF sample maintained continuous function for at least 15 h. This work provides new guidance for modification with PCN materials as a means of obtaining high photocatalytic efficiency and sheds light on the effect of appended pyridine rings on a CTF.