Highly Mesoporous MoO₃ Catalysts for Electrophilic Aromatic Substitution

Area of Science:

• Materials Science
• Catalysis
• Nanotechnology

Background:

• Developing efficient solid acid catalysts is crucial for various chemical transformations.
• Molybdenum oxide (MoO3) is a promising material, but its catalytic activity is often limited by its structure and surface area.

Purpose of the Study:

• To develop a straightforward synthesis method for highly mesoporous molybdenum oxide (MoO3) with enhanced catalytic properties.
• To evaluate the synthesized MoO3 catalyst's performance in electrophilic substitution reactions.

Main Methods:

• Synthesis of mesoporous MoO3 using inverse micelles and molybdenum-oxo cluster formation.
• Characterization of the catalyst's phase purity, stability, and crystallinity using TGA, XRD, XPS, EPR, Raman, and UV-vis spectroscopy.
• Evaluation of catalytic activity via ammonia chemisorption studies and electrophilic substitution of benzyl alcohol with toluene.

Main Results:

• The synthesized MoO3 catalyst is stable, crystalline, and phase-pure.
• Chemisorption studies revealed a 65-fold increase in activity compared to commercial catalysts (1270 μmol/g vs 22 μmol/g).
• Electrophilic substitution achieved >99% conversion and ~80% selectivity, with high turnover numbers (TON=115, TOF=38).

Conclusions:

• A facile synthesis route yields a highly active and stable mesoporous MoO3 catalyst.
• The catalyst demonstrates excellent performance in solid acid-catalyzed electrophilic substitution reactions.
• The study proposes a reaction mechanism and highlights substrate scope preferences.