Enhanced Green Hydrogen Generation via Photocatalytic Water Splitting Using V-Doped Ti-Squarate MOFs

Area of Science:

• Materials Science
• Photocatalysis
• Green Chemistry

Background:

• Metal-organic frameworks (MOFs) show promise for photocatalysis but often require cocatalysts or suffer from low efficiency.
• Defect engineering and metal doping are strategies to tune MOF properties for enhanced photocatalytic performance.
• Squarate-based MOFs, specifically IEF-11, are explored for their potential in solar fuel production.

Purpose of the Study:

• To enhance the photocatalytic activity of squarate-based MOFs (IEF-11) for green hydrogen generation via water splitting.
• To investigate the effects of defect engineering (mesopore formation) and vanadium (V) doping on IEF-11's properties and performance.
• To achieve efficient photocatalytic water splitting without the need for cocatalysts.

Main Methods:

• Microwave (MW)-assisted synthesis was employed to improve the textural properties of IEF-11(Ti), increasing surface area and creating mesopores via defect aggregation (linker vacancies).
• Vanadium was doped into the IEF-11(Ti) structure at varying concentrations (0-100%) to modify its optical and electronic properties.
• The synthesized MOFs were tested as photocatalysts for the hydrogen evolution reaction and overall water splitting under simulated sunlight, with theoretical calculations supporting experimental observations.

Main Results:

• Microwave synthesis significantly increased the surface area of IEF-11(Ti) by four-fold, creating mesopores due to linker vacancies.
• Vanadium doping progressively reduced the optical band gap of IEF-11, enabling absorption in the visible light region.
• The MW-synthesized IEF-11(Ti) doped with 11% V exhibited the highest hydrogen evolution activity (1053 μmol g^-1 h^-1), outperforming undoped IEF-11(Ti) (536 μmol g^-1 h^-1) due to improved charge separation and band alignment. It also showed a 30% increase in overall water splitting activity (83 μmol g^-1 h^-1).

Conclusions:

• Defect engineering (artificial porosity) and vanadium doping are effective strategies for enhancing the photocatalytic performance of squarate-based MOFs for water splitting.
• The study reports the first vanadium-doped squarate frameworks and demonstrates their high efficiency in photocatalytic water splitting without cocatalysts.
• Optimized V-doping in MW-synthesized IEF-11(Ti) leads to superior photocatalytic activity by facilitating charge transfer and reducing electron-hole recombination.