CO2 chemisorption and activation on carbon nitride with less amino groups boost CO2 photoreduction

CO2 chemisorption and activation are two crucial factors that can significantly impact the overall CO2 conversion efficiency. However, achieving effective modulation of these processes in metal-free photocatalysts has proven to be challenging. In this study, we present a novel approach for activating CO2 molecules by selectively removing some amino groups at the boundary of carbon nitride (CN). By doing so, we observed a concentration of photogenerated electrons at the nitrogen atoms neighboring the eliminated –NH2 group. This electron concentration enhances the chemisorption and activation of CO2, resulting in lowered energy barriers for the rate-determining step from CO2 to *COOH. Interestingly, we found that only the nitrogen atoms adjacent to the removed –NH2 group in CN serve as catalytic sites, in contrast to all the nitrogen atoms neighboring the –NH2 group in CN–NH2. As a result, CN exhibits superior catalytic efficiency, with a turnover frequency (TOF) for CO that is 23.11 times higher than that of CN–NH2 under identical conditions.