Biomass-Derived Single Zn Atom Catalysts: The Multiple Roles of Single Zn Atoms in the Oxidative Cleavage of C-N Bonds

The C-N bond cleavage represents one kind of important organic and biochemical transformation, which has attracted great interest in recent years. The oxidative cleavage of C-N bonds in N,N-dialkylamines into N-alkylamines has been well documented, but it is challenging in the further oxidative cleavage of C-N bonds in N-alkylamines into primary amines due to the thermally unfavorable release of alpha-position H from N-C alpha-H and the paralleling side reactions. Herein, a biomass-derived single Zn atom catalyst (ZnN4-SAC) was discovered to be a robust heterogeneous non-noble catalyst for the oxidative cleavage of C-N bonds in N-alkylamines with O2 molecules. Experimental results and DFT calculation revealed that ZnN4-SAC not only activates O2 to generate superoxide radicals (center dot O2-) for the oxidation of N-alkylamines to generate imine intermediates (C=N), but the single Zn atoms also served as the Lewis acid sites to promote the cleavage of C=N bonds in imine intermediates, including the first addition of H2O to generate alpha-hydroxylamine intermediates and the following C-N bond cleavage via a H atom transfer process.