Fabricating intramolecular donor-acceptor system via covalent bonding of carbazole to carbon nitride for excellent photocatalytic performance towards CO2 conversion.

Construction of g-C 3 N 4 and carbazole based D-A structure with enhanced charge carrier separation efficiency for efficient photoreduction of CO 2. [Display omitted] • A new D-A structure (g-CN-0.01Dbc) based on g-C 3 N 4 and carbazole was prepared. • The D-A structure led to enlarged the light response region and reduced bandgap. • The spatial separation of charge carrier resulted from D-A structure remarkably reduced the recombination of electron-hole pair. • The photoelectric properties and catalytic performance of g-CN-0.01Dbc were significantly improved. Photocatalytic conversion of CO 2 into hydrocarbon fuels is an ideal technology of mitigating greenhouse effect caused by excessive emission of CO 2. However, the high recombination rate of electron-hole pairs and limited charge carriers transport speed constrained the catalytic performance of many semiconductor catalysts. In this contribution, a series of carbon nitride (g-CN) samples with intramolecular donor-acceptor (D-A) system were successfully prepared by introducing organic donor into their structures. Characterization results confirmed that carbazole was successful connected to the structure of g-CN via chemical bond. The formation of intramolecular D-A system greatly enlarged the light response region of g-CN-xDbc. In addition, a new charge transfer transition mode was formed in g-CN-0.01Dbc due to the incorporation carbazole, which enable it to use light with energy lower than the intrinsic absorption of g-CN. Meanwhile, the D-A structure led to the spatial separation of electrons and holes in g-CN-xDbc and significantly decreased the recombination rate of electron-hole pairs. The g-CN-0.01Dbc presented the best catalytic performance and the CO evolution rate was 9.6 times higher than that of g-CN. Moreover, the reaction was performed in water without any additive, which made it green and sustainable. DFT simulation confirmed the D-A structure and charge carrier migration direction in the prepared samples. [ABSTRACT FROM AUTHOR]