Influence of TiO2 phases and functional groups on photocatalytic reduction of nitroaromatics

Abstract

Photocatalytic organic transformations have emerged as environmentally sustainable alternatives to traditional synthesis routes. This study delves into the intricacies of photocatalytic reduction of nitroaromatics using bare TiO2 materials, shedding light on critical factors that govern this green and sustainable transformation. Our systems reveal very promising conversion and selectivity levels, consistently exceeding 90% across 13 diverse nitroaromatic substrates. The position and nature of functionalities (e.g., electron withdrawing/donating groups) within the nitroaromatic molecule, as well as the crystal phase of TiO2 (anatase/rutile), emerged as crucial determinants of reaction efficiency. Furthermore, the pivotal role of methanol in this system is highlighted, not only facilitating efficient hole scavenging and byproduct prevention but also multiplying reduction efficiency. This work emphasizes the significance of careful solvent selection, crystal phase optimization, and the role of functional groups as the so-called external factors in optimizing photocatalytic reactions for sustainable and environmentally friendly synthesis.