13. Highly Selective Photoreduction of CO2 with Suppressing H2 Evolution over Monolayer Layered Double Hydroxide under Irradiation above 600 nm

Tan, L., Xu, S. M., Wang, Z., Xu, Y., Wang, X., Hao, X., Bai, S., Ning, C., Wang, Y., Zhang, W., Jo, Y. K., Hwang, S. J., Cao, X., Zheng, X., Yan, H., Zhao, Y.*, Duan, H.*, Song, Y. F.*
Angew. Chem. Int. Ed. 2019, 58, 11860-11867.
DOI: 10.1002/anie.201904246

Abstract
Although progress has been made to improve photocatalytic CO₂ reduction under visible light (λ>400 nm), the development of photocatalysts that can work under a longer wavelength (λ>600 nm) remains a challenge. Now, a heterogeneous photocatalyst system consisting of a ruthenium complex and a monolayer nickel-alumina layered double hydroxide (NiAl-LDH), which act as light-harvesting and catalytic units for selective photoreduction of CO₂ and H₂O into CH₄ and CO under irradiation with λ>400 nm. By precisely tuning the irradiation wavelength, the selectivity of CH₄ can be improved to 70.3 %, and the H₂ evolution reaction can be completely suppressed under irradiation with λ>600 nm. The photogenerated electrons matching the energy levels of photosensitizer and m-NiAl-LDH only localized at the defect state, providing a driving force of 0.313 eV to overcome the Gibbs free energy barrier of CO₂ reduction to CH₄ (0.127 eV), rather than that for H₂ evolution (0.425 eV).