Photoredox Coupling of CO 2 Reduction with Benzyl Alcohol Oxidation over Ternary Metal Chalcogenides (Zn m In 2 S 3+m , m = 1-5) with Regulable Products Selectivity.

Integrating photocatalytic CO 2 reduction with selective benzyl alcohol (BA) oxidation in one photoredox reaction system is a promising way for the simultaneous utilization of photogenerated electrons and holes. Herein, Zn m In 2 S 3+m (m = 1-5) semiconductors (ZnIn 2 S 4 , Zn 2 In 2 S 5 , Zn 3 In 2 S 6 , Zn 4 In 2 S 7 , and Zn 5 In 2 S 8 ) with various composition faults were synthesized via a simple hydrothermal method and used for effective selective dehydrocoupling of benzyl alcohol into high-value C-C coupling products and reduction of CO 2 into syngas under visible light. The absorption edge of Zn m In 2 S 3+m samples shifted to shorter wavelengths as the atomic ratio of Zn/In was increased. The conduction band and valence band position can be adjusted by changing the Zn/In ratio, resulting in controllable photoredox ability for selective BA oxidation and CO 2 reduction. For example, the selectivity of benzaldehyde (BAD) product was reduced from 76% (ZnIn 2 S 4 , ZIS1) to 27% (Zn 4 In 2 S 7 , ZIS4), while the selectivity of hydrobenzoin (HB) was increased from 22% to 56%. Additionally, the H 2 formation rate on ZIS1 (1.6 mmol/g/h) was 1.6 times higher than that of ZIS4 (1.0 mmol/g/h), and the CO formation rate on ZIS4 (0.32 mmol/g/h) was three times higher than that of ZIS1 (0.13 mmol/g/h), demonstrating that syngas with different H 2 /CO ratios can be obtained by controlling the Zn/In ratio in Zn m In 2 S 3+m . This study provides new insights into unveiling the relationship of structure-property of Zn m In 2 S 3+m layered crystals, which are valuable for implementation in a wide range of environment and energy applications.