CuXBpy-MOF/TiO₂ (X = I or Br) Composite Nanomaterials for Photocatalytic Hydrogen Generation

Developing composites based on Metal-Organic Frameworks (MOFs) with enhanced photocatalytic properties for green hydrogen production offers a promising solution to energy and environmental challenges. This study focuses on the synthesis of copper-based MOFs (namely CuBrbpy and CuIbpy) combined with TiO₂ to form heterojunction nanocomposites with improved photocatalytic activity for hydrogen generation. Triethylamine (TEA) was used as a hole scavenger and the synthesized materials were characterized by different techniques: ultraviolet-visible (UV-Vis) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), transmission-electron microscopy (TEM), and photoelectrochemical techniques. Time-resolved microwave conductivity (TRMC) was used to investigate the charge-carrier dynamics. The photocatalytic hydrogen production rate of the nanocomposites was evaluated under UV-visible light irradiation and quantified using micro-gas chromatography (Micro-GC). The CuIbpy/TiO₂ and CuBrbpy/TiO₂ composites, with an optimized mass ratio of 1:20, exhibited the highest photocatalytic hydrogen evolution rates of 7.8 mmol g^-1 h^-1 and 7.0 mmol g^-1 h^-1, respectively. The enhanced photocatalytic activity is mainly associated with improved interfacial charge transfer and charge-carrier separation due to the MOF/TiO₂ heterojunction. Cycling experiments showed a slight decrease of activity probably due to copper and nitrogen leaching, as confirmed by post XPS analysis. These findings also demonstrate that the ligand environment significantly governs the electronic interactions and photocatalytic behaviour of Cu-MOF/TiO₂ composite systems.