Phenanthridine-based Covalent Organic Frameworks for Boosting Overall Solar H₂O₂ Production

Area of Science:

• Materials Science
• Photocatalysis
• Green Chemistry

Background:

• Solar-driven hydrogen peroxide (H2O2) production via oxygen reduction reaction (ORR) and water oxidation reaction (WOR) is sustainable but kinetically limited.
• Developing efficient photocatalysts with effective active centers is crucial for overcoming these limitations.

Purpose of the Study:

• To synthesize novel phenanthridine-based covalent organic frameworks (PD-COFs) for enhanced H2O2 photoproduction.
• To investigate the role of phenanthridine units in modulating charge carrier dynamics and reaction intermediates for improved H2O2 synthesis.

Main Methods:

• Synthesis of phenanthridine-based covalent organic frameworks (PD-COF1 and PD-COF2) and a non-phenanthridine counterpart (AN-COF).
• Photocatalytic H2O2 production experiments under Xe lamp and natural sunlight in air and pure water without sacrificial agents.
• Experimental and theoretical analyses to elucidate the mechanism of charge carrier modulation and intermediate generation.

Main Results:

• PD-COF1 and PD-COF2 exhibited significantly enhanced H2O2 photogeneration rates compared to AN-COF.
• PD-COF2 achieved H2O2 photoproduction rates of 6103 μmol g⁻¹ h⁻¹ (Xe lamp) and 3646 μmol g⁻¹ h⁻¹ (sunlight).
• Phenanthridine units were shown to optimize charge carrier dynamics and favor key intermediates (OOH* and OH*) for ORR and WOR.

Conclusions:

• The incorporation of phenanthridine units into COFs effectively enhances solar-driven H2O2 production.
• This study demonstrates the novel use of neutral phenanthridine as a photooxidation unit for 2e⁻ WOR in H2O2 photoproduction.
• The developed PD-COFs represent promising photocatalysts for efficient and sustainable H2O2 evolution.