Solar Selective Photooxidation of Veratryl Alcohol by Suppression of Reactive Oxygen Species Through Band Modulation in the BiOI/Bi₄Ti₃O₁₂ Heterojunction

Lignin valorization through heterogeneous photocatalysis is a promising pathway for obtaining value-added products, including chemical building blocks, biofuels, etc. However, several challenges still demand attention and resolution in this field. One of the key parameters in the heterogeneous photocatalytic process is the synthesis of efficient photocatalysts that can accomplish efficient and selective reactions. Selective conversion of lignin can be achieved by using heterojunction photocatalysts which can efficiently separate charge carriers' and promote selective reactions by band structure modulation. This work details a straightforward approach for synthesizing heterojunction photocatalysts based on Bi₄Ti₃O₁₂ and BiOI involving the hydrothermal and co-precipitation methods. Additionally, the synthesized composites were employed in the selective oxidation of veratryl alcohol, a lignin-derived model compound, to produce high-value-added veratraldehyde. The experimental results showed that the BiOI/Bi₄Ti₃O₁₂ heterojunction (12.5 mol % BiOI) showed superior activity with a veratraldehyde yield of 5.4 and 27.2 times higher than those of Bi₄Ti₃O₁₂ and BiOI, respectively. The mechanistic studies revealed that the improved activity and selectivity were due to the enhanced charge carriers' separation and the suppression of reactive oxygen species formation through modulation of band structure. This study allows a green approach to lignin-derived biomass valorization to obtain high-value chemicals.