Surface Engineering of 2D Metal-Porphyrin Metal-Organic Frameworks Z-Scheme Heterostructure for Boosting and Stable...

How to improve the stability and activity of metal-organic frameworks is an attractive but challenging task in energy conversion and pollutant degradation of metal-organic framework materials. In this paper, a facile method is developed by fabricating titanium dioxide nanoparticles (TiO₂ NPs) layer on 2D copper tetracarboxylphenyl-metalloporphyrin metal-organic frameworks with zinc ions as the linkers (ZnTCuMT-X, "Zn" represented zinc ions as the linkers, the first "T" represented tetracarboxylphenyl-metalloporphyrin (TCPP), "Cu" represented the Cu²⁺ coordinated into the porphyrin macrocycle, "M" represented metal-organic frameworks, the second "T" represented TiO₂ NPs layer, and "X" represented the added volume of n-tetrabutyl titanate (X = 100, 200, 300 or 400)). It is found that the optimized ZnTCuMT-200 showed greatly and stably enhanced H₂ generation, which is ≈28.2 times and 47.0 times as high as those of the original ZnTCuM and TiO₂, respectively. Combined with the results of free radical capture, X-ray photoelectron spectra (XPS), electron spin resonance (ESR), and theoretical calculation, a direct Z-scheme electron transfer mechanism is achieved to fully explain the enhanced photocatalytic performance. It demonstrates that facilely designing Z-scheme heterostructures based on porphyrin MOFs modified with an inorganic semiconductor layer can be an advantageous strategy for enhancing the stability and activity of photocatalytic hydrogen evolution.