Benzophenone-Based Polymers and Covalent Organic Framework for Photocatalytic Molecular Oxygen Activation

Area of Science:

• Materials Science
• Photochemistry
• Organic Chemistry

Background:

• Effective photosensitization relies on molecular engineering for sustained photochemical processes.
• Developing heavy-atom-free (HAF) strategies to boost photosensitizer activity is a key challenge.

Purpose of the Study:

• To introduce a novel HAF strategy for enhanced photosensitization using benzophenone-rich components.
• To investigate the photoactivity and catalytic applications of new 3D polymers and a 2D covalent organic framework (COF).

Main Methods:

• Incorporation of benzophenone-rich units into 3D polymers (BQP1, BQP2) and a 2D COF (BQ-TMT COF).
• Evaluation of charge carrier dynamics and intersystem crossing enhancement.
• Testing photocatalytic activity for O2 activation, sulfide oxidation, boronic acid hydroxylation, and amine oxidation.
• Fabrication and testing of a BQ-TMT COF-based photoelectrode for photocurrent generation and hydrogen production.

Main Results:

• The BQ-TMT COF demonstrated efficient photocatalytic activation of molecular oxygen, producing singlet oxygen (1O2) and superoxide radicals (O2•−) with high efficiency and recyclability.
• Selective photocatalytic oxidation of sulfides via 1O2 and oxidation of boronic acids and amines via O2•− were achieved.
• The BQ-TMT COF-based photoelectrode exhibited a photocurrent of ~20.7 μA·cm−2 and a high rate of photocatalytic hydrogen production.

Conclusions:

• The developed benzophenone-rich COF serves as an efficient HAF heterogeneous photosensitizer.
• Molecular engineering of these materials significantly enhances photoactivity for small molecule activation and energy conversion.