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.