Research progress on NH₂-MIL-125(Ti)-based photocatalytic materials: from synthesis strategies and modification engineering to environmental and energy applications

NH₂-MIL-125(Ti), a representative titanium-based metal-organic framework, has attracted considerable attention in environmental remediation and energy conversion owing to its integrated advantages, including electron transfer through Ti-O clusters, amino-group-induced visible-light response, and adsorption enrichment enabled by its porous framework. However, single-component NH₂-MIL-125(Ti) still suffers from several intrinsic limitations, such as rapid recombination of photogenerated charge carriers, insufficient visible-light utilization, limited stability in aqueous environments, and unsatisfactory reaction selectivity, which restrict its further practical applications. To address these challenges, this review systematically summarizes recent advances in NH₂-MIL-125(Ti)-based materials from the perspectives of synthesis strategies, structural regulation, and photocatalytic applications. Particular emphasis is placed on the effects of synthetic parameters, including titanium sources, solvents, reaction time, and modulators, on crystal morphology, exposed crystal facets, and crystallinity. In addition, the mechanisms and applicable scenarios of various modification strategies are comparatively discussed, including morphology/facet engineering, defect engineering, metal or ligand modification, and heterostructure construction. Furthermore, this review summarizes the application characteristics of NH₂-MIL-125(Ti)-based materials in organic pollutant degradation, NO removal, heavy metal reduction, photocatalytic hydrogen production, CO₂ reduction, nitrogen fixation for ammonia synthesis, and green organic synthesis. Comprehensive analysis indicates that heterostructure construction is currently the most versatile modification strategy, as it can simultaneously enhance light absorption, interfacial charge separation, and redox capability. By contrast, morphology/facet regulation, defect engineering, and metal/ligand modification are more suitable as synergistic approaches for specific photocatalytic reactions. Finally, future perspectives are proposed in terms of structural stability, green and scalable synthesis, adaptability to complex reaction systems, and standardization of mechanistic analysis, aiming to provide guidance for the rational design of efficient NH₂-MIL-125(Ti)-based photocatalytic systems.