Preparation of Ti₁Li₃Al₂-LDHs/g-C₃N₄ composites and its photocatalytic properties in CO₂-toluene reaction system

Photocataltyic reduction of CO₂ is one of the promising routes in CO₂ conversion and utilization, but the very low CO₂ conversion rate is the biggest hurdle for the process. Developing a new CO₂ reduction reaction system and improving the visible light utilization and separation efficiency of photogenerated electrons and holes are effective ways to solve the above problems. In this work, we designed a CO₂-toluene coupling reaction system to promote the CO₂ reduction reaction. The Ti₁Li₃Al₂-layered dihydroxides (LDHs)/graphite phase carbon nitride (g-C₃N₄) composite with heterojunction structure were synthesized by electrostatic assembly method. And the photoelectric property and photocatalytic properties of Ti₁Li₃Al₂-LDHs/g-C₃N₄ composite were explored in CO₂-toluene reduction reaction system. The results show that CO₂ is reduced to CO, and toluene is oxidized to benzyl alcohol, benzaldehyde and benzyl benzoate in the photocataltyic coupling reaction system. Benzaldehyde and benzyl alcohol content can reach 4.80 and 4.70 mmol/g_cat. This is mainly because the g-C₃N₄ can extend the absorption of Ti₁Li₃Al₂-LDHs from the ultraviolet region to the visible region, and improve the dispersion of Ti₁Li₃Al₂-LDHs which provide more active sites for photocatalytic reactions. Moreover, the S-type heterojunction is formed in the interface of Ti₁Li₃Al₂-LDHs/g-C₃N₄, which is conducive to the transfer of photogenerated electrons at the interface and improves the separation efficiency of photogenerated electrons and holes. And toluene can be used as an organic substrate to accelerate the rate of hole consumption and stimulate the CO₂ reduction reaction. This work provides a new idea for the synergistic reaction between CO₂ reduction and small molecular organics.