Bimetallic (Fe-Ga) Metal-Organic Frameworks for Tailoring Peroxidase-Like Activity: An Approach for Methane Partial...

Area of Science:

• Materials Science
• Catalysis
• Chemical Engineering

Background:

• Methane oxidation to higher-value products under mild conditions is challenging due to C-H bond stability.
• Metal-organic frameworks (MOFs) show promise for methane oxidation, but metal active site leaching and degradation in oxidative environments limit their use.
• Stabilizing metal sites within MOFs is crucial for developing robust catalysts.

Purpose of the Study:

• To develop a novel, structurally engineered metal-organic framework (MOF) for enhanced methane oxidation.
• To improve the stability and catalytic activity of MOFs by incorporating gallium (Ga) doping into iron (Fe)-based MOFs.
• To investigate the catalytic performance and stability of bimetallic Fe-Ga MOFs for selective methane oxidation.

Main Methods:

• Synthesized a series of bimetallic MOFs with varying Fe and Ga compositions, denoted as Fe_xGa_y-MOF, by doping Fe-MIL-88B with Ga³⁺.
• Evaluated the chemical stability of the synthesized MOFs in aqueous and oxidative conditions.
• Optimized reaction parameters including catalyst mass, temperature, and pressure for methane oxidation.

Main Results:

• The bimetallic Fe_xGa_y-MOF exhibited significantly enhanced stability and reduced metal leaching compared to the parent Fe-MIL-88B.
• Fe_0.3Ga_0.7-MOF demonstrated superior stability and catalytic activity, producing methanol, formic acid, and acetic acid with high productivity.
• Fe_0.3Ga_0.7-MOF achieved a 36% increase in oxygenate selectivity and a 95% reduction in CO₂ evolution, retaining activity over three cycles with minimal metal leaching (0.1%).

Conclusions:

• Structural engineering via Ga³⁺ doping effectively stabilizes Fe active sites in Fe-MIL-88B, creating robust bimetallic MOFs.
• The Fe_0.3Ga_0.7-MOF is a highly stable and selective catalyst for converting methane to valuable oxygenates under mild conditions.
• The findings highlight the potential of tailored MOF structures for efficient and sustainable methane valorization, with reactive oxygen species playing a key role in the reaction mechanism.