Recent advances in W18O49 Photocatalysts: Defect engineering, structural modulation and photocatalytic applications

W 18 O 49 , an oxygen-vacancy-rich semiconductor exhibiting strong localized surface plasmon resonance (LSPR), has emerged as a promising photocatalyst for solar energy conversion and environmental remediation. However, its practical application remains hindered by rapid charge-carrier recombination, slow surface reaction kinetics, and the difficulty of simultaneously optimizing oxygen vacancy (OV) concentration and plasmonic properties. To address these challenges, a variety of structural engineering strategies have been developed to regulate its electronic structure, interfacial charge transfer and surface reaction pathways. This review provides a critical overview of recent advances in the field, with particular emphasis on the mechanistic relationships among catalyst design, physicochemical properties and photocatalytic performance. Representative modification strategies, including morphology engineering, hetero−/homo-junction construction, co-catalyst loading and elemental doping are comprehensively analyzed to elucidate their distinct and complementary roles in regulating OVs, LSPR, charge-carrier dynamics and catalytic activity. The diverse photocatalytic applications of W 18 O 49 , including CO 2 reduction, alcohol dehydration, N 2 fixation and H 2 O 2 production are further discussed within a unified mechanistic framework that highlights the interplay between OVs, plasmonic effects and rational catalyst engineering. Finally, the current challenges, emerging opportunities and future research directions for the rational design of highly efficient and durable W 18 O 49 photocatalysts are discussed. This review aims to provide fundamental design principles and practical guidance for the development of next-generation W 18 O 49 photocatalysts for sustainable energy conversion and environmental remediation.