Photoreduction of nitrophenol using metal oxide-based nanocomposites: a green and efficient approach for aqueous environmental remediation

Phenolic compounds pose a significant hazard in water bodies due to their widespread presence. Among these, nitrophenol (NP) stand out as a distinct class of phenolic derivatives with high water solubility, causing contamination of aquatic ecosystems. A notably economical and environmentally judicious approach involves the reduction of NP to aminophenol (AP), particularly the conversion 4-NP to 4-AP. This specific transformation holds substantial value as 4-AP serves as a versatile precursor in pharmaceutical synthesis. This comprehensive review focuses on the photoreduction of NP into AP utilising various metal oxide photocatalysts. The integration of diverse dopants, cocatalysts, and the construction of heterojunction interfaces emerges as a pivotal strategy for augmenting the light-harvesting capacity of metal oxides. This review address (1) an exploration of diverse photocatalysts efficacious in NP reduction, (2) an analysis of factors exerting influence over photoreduction efficiency, and (3) an intricate examination of strategies employed for the modification of diverse metal oxide catalysts. Additionally, this review paper presents diverse future prospects to advance composite metal oxides for NP photoreduction.