Harnessing the Heavy-Atom Effect and Linkage Engineering in Isomorphic COFs for Enhanced H₂O₂ Photosynthesis

Area of Science:

• Materials Science
• Photocatalysis
• Organic Chemistry

Background:

• Photocatalytic covalent organic frameworks (COFs) performance depends on electronic structure and morphology.
• Heteroatom incorporation in COFs offers tunable optoelectronic properties for applications like H2O2 production.

Purpose of the Study:

• To synthesize and optimize COFs by tuning heteroatom type and position for enhanced H2O2 production.
• To investigate the role of sulfur heteroatoms and molecular structure on COF photocatalytic performance.

Main Methods:

• Synthesis of ten COFs across two categories with precise heteroatom tuning.
• Characterization of electronic and band structures to correlate with photocatalytic activity.
• Evaluation of H2O2 production rates and apparent quantum yields (AQY).

Main Results:

• Thiourea-based COF-127 achieved a high H2O2 production rate (6672 µmol g⁻¹ h⁻¹) and AQY (11.03%).
• Sulfur's heavy-atom effect enhanced spin-orbit coupling and triplet exciton generation.
• Sulfur introduction improved charge separation and migration, compensating for adsorption energy barriers.

Conclusions:

• A rational design paradigm for COF photocatalysts based on a 'heavy-atom foundation coupled with molecular structure optimization' was established.
• Synergistic effects of sulfur, heteroatom type, and linker geometry collectively modulate band structure, carrier dynamics, and reaction energetics.
• Optimized COFs show significant potential for efficient H2O2 production.