Nitrogen-doped porous carbons synthesized with low-temperature sodium amide activation as metal-free catalysts for oxidative coupling of amines to imines

Plant biomass are considered as good precursors for synthesizing carbons due to their abundance and non-toxicity. In the synthesis process, many activators are needed to endow carbons with abundant pore structure. However, the traditional activators are highly corrosive and reduce the nitrogen content of carbons, which is not conducive to their applications. Herein, we choose sodium amide (NaNH2), which is less corrosive and strongly nucleophilic, as activator. The research shows that NaNH2 can activate ginkgo leaves at relatively low temperature (500 °C) and obviously improve the structure and composition of their derived carbons. When used as catalysts for the oxidative coupling of benzylamine to imine, the carbon synthesized with the largest amount of NaNH2 activator exhibits the best performance, which can be attributed to the synergistic effects of high surface area, hierarchical structure and abundance active sites. Further, the catalytic performance of carbons derived from apricot leaves and poplar leaves activated by NaNH2 also increases with the increase in the NaNH2 dosage, which indicates that NaNH2 is a widely adaptable activator for plant biomass.