Fabrication of TiO₂/MOF Type II Heterojunctionby Growth of TiO₂ on Cr-Based MOF for Enhanced PhotocatalyticHydrogen Production

MOF-based heterojunctions can significantly enhance the efficiency of photocatalytic hydrogen production; however, the construction of efficient MOF-based heterojunctions remains a formidable challenge. In this study, we successfully developed a series of Type II MOF-based heterojunctions by growing TiO₂ on Cr-based MOF, thereby regulating the generation, separation, and transportation of photogenerated charge carriers to improve photocatalytic hydrogen evolution performance. Among these, the 23%TiO₂/MIL-101(Cr) photocatalyst exhibited the highest photocatalytic hydrogen production activity, achieving 884.01 μmol g^–1 in just 5 h, which is 6.8 and 6.0 times that of pure MIL-101(Cr) and TiO₂, respectively. Additionally, the 23%TiO₂/MIL-101(Cr) photocatalyst demonstrated excellent cyclic stability. Tiny TiO₂ particles were proven mainly deposited on the MIL-101(Cr) surface by N₂ sorption isotherm analyses, transmission electron microscopy (TEM), high-resolution TEM, high-angle annular dark field scanning transmission electron microscopy, etc. Characterization techniques such as in situ XPS confirmed the formation of the TiO₂/MIL-101(Cr) Type II heterostructure. Band structure analysis indicates that the 23%TiO₂/MIL-101(Cr) meets the thermodynamic requirements for photocatalytic hydrogen production. Furthermore, transient photocurrent measurements, electrochemical impedance analysis, and photoluminescence reveal that the 23%TiO₂/MIL-101(Cr) possesses superior capabilities in photogenerated charge carrier generation, separation, and transport, resulting in efficient photocatalytic hydrogen production from a kinetic perspective. This research offers valuable insights into the preparation of MOF-based heterojunctions and the development of efficient photocatalysts for hydrogen production.