Facile implantation of imidazole-ring into graphitic carbon nitride for efficient photocatalytic hydrogen production

Herein, two carbon nitrides implanted with imidazole-rings were prepared by heating a mixture containing urea and imidazolium chloride, which were denoted as PI-CN and MI-CN by using poly-(imidazolium-methylene) chloride (PImM) and 1-methylimidazolium chloride (MIm) as imidazolium salts, respectively. PImM is more effective than MIm in extending the delocalization of the pi-electron conjunction system of carbon nitride by implanting imidazole-rings. As a result, PI-CN shows a high hydrogen evolution rate of 4659 mu mol h(-1) g(-1) (lambda > 420 nm), which is 8.4 and 27.9 times higher than that of MI-CN and pristine carbon nitride (BCN) prepared in the absence of imidazolium chloride, and is ascribed to the remarkably improved visible light absorption and notably enhanced charge separation by extended delocalization of pi-electrons resulting from the use of polyimidazolium ion. This work presents a new method to efficiently delocalize the pi-electron conjunction system of carbon nitride.