B,F Co-doped carbocatalysts with dual-active-sites for acceptorless dehydrogenation of N-heterocycles under room temperature

Abstract

Metal-free carbocatalysts have sparked intensive interest in oxidative dehydrogenation. However, efficient metal-free carbocatalysts for non-oxidative dehydrogenation with H2 liberation under mild conditions has rarely been reported. Herein, we successfully fabricated B,F co-doped nitrogen-assembly carbons (BF-NCs), which display outstanding catalytic performance and reaction generality in acceptorless dehydrogenation of N-heterocycles at mild and even at room temperatures, observably outperforming that of undoped NCs or single-doped B-NCs (B-NCs). Specifically, dual-active-sites were achieved in BF-NCs, i.e., the closely-placed graphitic nitrogen (CGN) and the pyridinic N banded BFx. The results of kinetic analysis and DFT directly reveal that the dual-active-sites on carbocatalysts lower the energy barriers for tetrahydroquinoline (THQ) dehydrogenation, thereby accelerating H2 liberation even at room temperature. BF-NC shows promising recyclability and an ability to achieve 98.2% product yield without sacrificing efficacy in a 50-fold scale-up experiment, making the cost-effective and robust carbocatalysts a great contender for H2 liberation in practical industrial application.