Defect-Rich Core-Shell Carbon Derived from Ionic Liquid for Direct Synthesis of Imines

摘要

Development of metal-free catalysis in chemical transformation is highly desirable due to its significant inherent advantages compared with conventional metal or metal oxide catalysts but challenging. Herein, ionic liquid 1-ethyl-3-methylimidazolium dicyanamide and sodium tetraphenylborate were employed as joint precursors to facilely prepare micro-mesoporous core-shell carbon with specific surface area up to 2870m~2g~(-1), consisting of smooth unpenetrated shell and secondary hollow spherical carbon core. The as-obtained core-shell carbon as metal-free catalyst exhibited good performance for self-coupling and cross-coupling of amines to achieve the corresponding symmetry and asymmetry imines under mild and neat conditions. Excitingly, for the challenging aliphatic amines, the desired imines were achieved in our case in 55.9% yield. The nearly linearly correlation between imine yield and ID/IG indicated that the resulting defects from departure of heter-oatoms during pyrolysis may be active site.