Controllable photooxidation of 1-phenylethanol integrated with hydrogen evolution by a polyoxometalate/ZnIn₂S₄/WO₃ catalytic system

The photocatalytic oxidation of 1-phenylethanol coupling with hydrogen evolution represents a promising strategy for the full utilization of the photogenerated electrons and holes to accomplish the maximum conversion of solar energy into chemical energy. To date, however, the controllable of reaction path and product distribution has yet not to be unrevealed. Herein, we report an efficient coupled catalytic system composed of ZnIn₂S₄/WO₃ S-scheme heterojunction and Ni-containing polyoxometalate ([Ni₄(H₂O)₂(PW₉O₃₄)₂]¹⁰⁻ (Ni₄P₂)), which exhibited excellent photocatalytic activities towards the oxidation valorization of 1-phenylethanol coupling with hydrogen evolution. The addition of Ni₄P₂ can efficiently control the product distribution. Specifically, 1-phenylethanol was preferentially converted to pinacol (86.0% selectivity) via C–C coupling over ZnIn₂S₄/WO₃ S-scheme heterojunction accompanied by hydrogen production (202.4 μmol), whereas it would be converted to acetophenone (93.8% selectivity) by photogenerated holes with concomitant hydrogen formation (183.1 μmol) over the coupled Ni₄P₂/ZnIn₂S₄/WO₃ catalytic system. Mechanism studies revealed that the hydrogen evolution cocatalyst Ni₄P₂, with its excellent electron storage capacity, can compete with the oxidation product acetophenone for electrons, and thus its addition can significantly inhibit the reduction of acetophenone, resulting in the inability to generate the coupling product pinacol.