Defect engineered Ti-MOFs and their applications†

Titanium-based metal–organic frameworks (Ti-MOFs) hold great potential for applications in photocatalysis and other fields, owing to Ti's abundant reserves, low toxicity, and excellent photocatalytic and redox activity. However, Ti's strong affinity for oxygen often leads to Ti-MOFs being fully coordinated with ligands, which limits their catalytic and separation performance. Defect engineering provides an effective strategy to enhance the functionality of MOFs by introducing structural imperfections. Despite this, the synthesis of new Ti-MOFs and the incorporation of defects remain challenging due to the complex hydrolysis and reaction processes of Ti precursors and the uncertainty of Ti cluster formation. This review categorizes Ti-MOFs according to their diverse cluster structures, which play a key role in the development of new frameworks and defect engineering. It also examines various defect construction methods and their applications. Finally, insights from defect-engineered Zr-MOFs are discussed to inspire future advancements in the synthesis and application of defective Ti-MOFs.