A Comprehensive Review on Advancements in Photocatalytic Applications of Nanostructured Metal Oxides Toward Environmental Remediation

The increasing energy crisis and environmental contamination have become one of the most pressing global challenges, prompting the advancement of eco‐friendly and effective advanced treatment technologies. Although photocatalysis enabled by semiconducting materials has garnered intense research interest for pollution remediation, large‐scale application of widely studied semiconductor photocatalysts remains constrained by inefficient utilization of the visible‐light, fast recombination of charge carriers, and limited operational stability. This review highlights and critically evaluates the latest developments in nanostructured oxide semiconductor photocatalysts and their composites, addressing current research gaps by integrating synthesis methodologies, photocatalytic activity, and crystal structure design. Innovative synthesis methodologies, such as sol–gel, hydrothermal, co‐precipitation, and sonochemical techniques, are critically analyzed considering their benefits and associated limitations. The review elucidates mechanisms of photocatalysis, highlighting advanced heterojunction engineering and rational heterostructure design to increase absorption of light and suppress rapid electron–hole recombination. Recent advances in addressing environmental pollution are critically investigated via the remediation of toxic heavy metal ions, degradation of organic dyes, CO 2 reduction, pharmaceutical pollutant degradation, and nitrogen oxide (NO x ) reduction. Additionally, major challenges, practical constraints, and future perspectives are critically discussed to accelerate the development of effective, durable, high‐performance, and scalable photocatalytic systems. By incorporating transformative developments by bridging structure, properties, and photocatalytic performance, this review critically examines key insights and advanced design approaches for future‐oriented metal oxide photocatalytic technologies for next‐generation environmental remediation.