Photocatalytic Hydrogenation-Breaking of the C≡N Bond in Acetonitrile

The direct photocatalytic conversion of alkylnitriles through C≡N bond cleavage to alkanes and alkenes is a model case for challenging triple bond activation and could expand the toolbox of chemistry. Herein, we report the visible-light-driven photochemical complete reduction of the C≡N bond of acetonitrile into ethene/ethane and ammonia using a composite photocatalyst consisting of Cd0.6Zn0.4S and ZIF-67. The optimal photocatalyst shows the highest C≡N bond cleavage efficiency, with a formation rate of 422.2/206.1 μmol g–1 h–1 for the final reduction product (ethene/ethane). This is 463/229 times that of pure Cd0.6Zn0.4S. Isotopic-labeling experiments and liquid in situ attenuated total reflection infrared absorption spectra (ATR-IRAS) results confirm the cleavage mechanism of the C≡N bond via the nitrile hydrogenation-nitrile breaking process. Integrated photoelectric characterization and density functional theory (DFT) calculations attribute the high performance to the facilitated charge separation and a reduced energy barrier for hydrogenation in the composite photocatalyst. This study not only presents an innovative approach for acetonitrile conversion under mild reaction conditions but also provides a promising example for breaking C≡N bonds for photocatalytic cleaning of organic nitrile wastes.