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.