Cu-Based MOF/TiO₂ Composite Nanomaterials for Photocatalytic Hydrogen Generation and the Role of Copper

The development of active and durable photocatalysts without noble metals for green hydrogen generation is a major challenge in photocatalysis. Herein, composite nanomaterials based on TiO₂ coupled with HKUST-1, a copper metal–organic framework, for hydrogen generation by photocatalysis using water and methanol as sacrificial agents are developed. To design a highly active composite, the mass ratios between HKUST-1 and TiO₂ are studied and optimized. The photoactive composite materials are characterized by TEM, UV–vis spectroscopy, FTIR, XRD, XPS, and photoelectrochemical studies. The charge carrier dynamics is also studied by time-resolved microwave conductivity and the crucial role of the copper is also investigated by XPS and electron paramagnetic resonance. DFT calculations are also used to understand the mechanism involved in H₂ generation. The findings reveal a high hydrogen evolution rate of HKUST-1/TiO₂ (5.11 mmol g⁻¹h⁻¹) for the first cycle with the mass ratio (1:20). This activity increases with cycling until surpassing the performance of the 1 wt.% Pt (TiO₂) material, used as a benchmark and known as a reference in terms of photocatalytic hydrogen production, and a rate of 13.24 mmol g⁻¹h⁻¹ is obtained after the sixth cycle.