Diversifying Single-Crystal Structures of Covalent Organic Polymers Through a Symmetry-Broken Strategy

Area of Science:

• Materials Science
• Organic Chemistry
• Catalysis

Background:

• Covalent organic polymers (COPs) grown via dative B←N bonds are promising materials.
• Synthesizing diverse COP structures from identical motifs to study performance variations is challenging.
• Reducing structural unit symmetry offers a strategy for creating varied COP architectures.

Purpose of the Study:

• To introduce a strategy for constructing diverse single-crystal COP structures using a reduced-symmetry motif.
• To investigate the photocatalytic performance of these COPs in hydrogen peroxide (H2O2) synthesis.
• To explore structure-property relationships by comparing 1D and 2D COP architectures.

Main Methods:

• Employed the 3-pyridyl-based tetrathiafulvalene motif (TTF-(3-py)4) with inherent asymmetry.
• Synthesized single-crystal COPs (CityU-61, CityU-62, CityU-63) under varying solvent conditions.
• Characterized COP structures and evaluated their performance in photocatalytic H2O2 production from water and air.

Main Results:

• Successfully constructed 1D zigzag (CityU-61), 1D nanobelt (CityU-62), and 2D layer (CityU-63) COP structures.
• The TTF-(3-py)4 motif's rotatable bonds and nitrogen deviation enabled diverse configurations.
• All synthesized COPs demonstrated excellent light absorption and redox activity for H2O2 synthesis.
• CityU-63 achieved a high H2O2 production rate of 10,488.9 µmol g⁻¹ h⁻¹, indicating superior photocatalytic efficiency.

Conclusions:

• Reduced symmetry in structural motifs is an effective strategy for generating diverse COP architectures.
• The synthesized COPs, particularly CityU-63, are highly efficient photocatalysts for H2O2 production.
• These findings advance the development of advanced materials for sustainable chemical synthesis.