Decoding the Role of Isolated Ga⁺ in PdGa@MFI Catalyst Promoting a Direct CO₂ Hydrogenation Path to DME

Area of Science:

• Catalysis
• Materials Science
• Chemical Engineering

Background:

• Direct CO2 hydrogenation to valuable chemicals like DME is crucial for carbon utilization.
• Controlling active site proximity and nature in catalysts remains a challenge for reaction efficiency.

Purpose of the Study:

• To develop a strategy for precise control over active site distance, proximity, and nature in zeolite catalysts.
• To enhance the direct CO2 hydrogenation pathway to dimethyl ether (DME).

Main Methods:

• Utilizing a one-pot synthesis and thermal-induced detachment of framework elements (e.g., Ga3+).
• Stabilizing PdGa alloys and Ga+ sites near Brønsted acid sites under reductive conditions.
• Employing time-resolved kinetic studies, in situ X-ray adsorption, and in situ/operando IR spectroscopy.

Main Results:

• Achieved high oxygenate production (42,864 gMeOH+DME·kgPd-1·h-1) with 80% selectivity (19% methanol/61% DME).
• Demonstrated superior performance compared to existing Pd-based CO2 hydrogenation catalysts.
• Confirmed the critical role of isolated Ga+ Lewis acid sites near Brønsted acid sites in stabilizing intermediates and facilitating DME formation.

Conclusions:

• The developed strategy effectively controls active sites for enhanced CO2 hydrogenation to DME.
• Zeolites play a vital role in metal confinement, stability, and proximity of active sites.
• Isolated Ga+ Lewis acid sites adjacent to Brønsted acid sites are key for efficient DME synthesis.