Navigating the Bio-Inspired Structure-Function Landscape: Spectroscopy Driven Finding of Hidden Radical Oxidation in...

Area of Science:

• Catalysis
• Materials Science
• Organic Chemistry

Background:

• Conventional acetophenone synthesis via Friedel-Crafts reactions is waste-intensive.
• Development of sustainable and efficient alternatives is crucial for green chemistry.
• Radical oxidation presents a promising, environmentally benign route for acetophenone production.

Purpose of the Study:

• To design and synthesize a novel cobalt porphyrin-based metalated porous organic polymer (Co@POR-POP) catalyst.
• To investigate the catalytic activity of Co@POR-POP for acetophenone production from styrene.
• To elucidate the reaction mechanism and catalyst structure-activity relationship.

Main Methods:

• Synthesis of Co@POR-POP catalyst.
• Acetophenone production via radical oxidation of styrene.
• Characterization using BET surface area analysis, X-ray absorption fine structure (XAFS) spectroscopy, and electron paramagnetic resonance (EPR) spectroscopy.
• Mechanistic studies using spin-trapping with DMPO and density functional theory (DFT) calculations.

Main Results:

• Co@POR-POP exhibits high surface area (650 m²g⁻¹) and bimodal pores.
• Achieved >90% yield of acetophenone with excellent selectivity under ambient conditions.
• XAFS and EPR studies confirmed isolated square-planar Co-N₄ active sites and radical intermediates.
• DFT calculations revealed a thermodynamically favorable reaction pathway with efficient O₂ activation.

Conclusions:

• Co@POR-POP is a highly active and selective catalyst for sustainable acetophenone production.
• The reaction proceeds via a radical-mediated mechanism involving O₂ activation facilitated by the catalyst's electronic structure.
• This work demonstrates the potential of metalated porous organic polymers for novel organic transformations.