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

Abstract

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 <i>N</i>,<i>N</i>-dialkylamines into <i>N</i>-alkylamines has been well documented, but it is challenging in the further oxidative cleavage of C-N bonds in <i>N</i>-alkylamines into primary amines due to the thermally unfavorable release of α-position H from N-C_α-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 <i>N</i>-alkylamines with O₂ molecules. Experimental results and DFT calculation revealed that ZnN₄-SAC not only activates O₂ to generate superoxide radicals (·O₂ ^-) for the oxidation of <i>N</i>-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 α-hydroxylamine intermediates and the following C-N bond cleavage via a H atom transfer process.