Symmetry Basis Engineered Covalent Organic Frameworks for Water Purification Under Ultralow Light Intensity.

Area of Science:

• Materials Science
• Environmental Science
• Chemistry

Background:

• Solar-to-chemical energy conversion is key for sustainable water purification but challenged by low sunlight intensity.
• Covalent organic frameworks (COFs) offer potential for photocatalysis but require optimized designs.

Purpose of the Study:

• To design and synthesize novel symmetric and asymmetric bipyridine-based COFs for enhanced solar-driven water purification.
• To investigate the structure-activity relationship of COFs in pollutant degradation under low-light conditions.

Main Methods:

• Synthesis of symmetric (Bby-COF) and asymmetric bipyridine-based COFs.
• Photocatalytic degradation of ofloxacin (OFL) under simulated and natural sunlight.
• Kinetic analysis and mechanistic studies involving superoxide radicals and photoexcited holes.

Main Results:

• The symmetric Bby-COF exhibited a significantly higher OFL removal rate (28.14 × 10⁻² min⁻¹) compared to the asymmetric counterpart (4.45 × 10⁻² min⁻¹).
• Bby-COF achieved complete OFL removal within 30-40 minutes under ultra-low light intensity (36 mW cm⁻²).
• A flow-through reactor demonstrated large-scale wastewater treatment potential, purifying 58.8 L consecutively.

Conclusions:

• Symmetry engineering in bipyridine-based COFs enhances charge density and electron sink effects, optimizing photocatalytic activity.
• The developed Bby-COF demonstrates high efficiency for solar wastewater treatment under challenging low-light conditions.
• This study presents a viable molecular strategy for translating laboratory photocatalysis to real-world applications.