Directional Concerted Proton-Electron Transfer in COFs for Efficient Photocatalytic H₂O₂ Production

Area of Science:

• Materials Science
• Catalysis
• Green Chemistry

Background:

• Photocatalytic two-electron oxygen reduction reaction (2e⁻ ORR) is key for sustainable H₂O₂ synthesis.
• Efficiency is limited by kinetic mismatches in proton and electron transfer at interfaces.
• Natural hydrogenases inspire strategies for efficient proton-electron translocation.

Purpose of the Study:

• To design a covalent organic framework (COF) for enhanced photocatalytic H₂O₂ production.
• To achieve directional concerted proton-electron transfer (DCPET) for improved reaction kinetics.
• To overcome limitations of conventional photocatalyst designs.

Main Methods:

• Synthesis of a catechol-triazine donor-acceptor (D-A) COF, 2,3-Dhta-Tt.
• Utilizing the COF's intrinsic electric field and proton-relay network for directed charge transport.
• Employing isotope labeling, operando spectroscopy, and DFT calculations for mechanistic studies.

Main Results:

• The 2,3-Dhta-Tt COF demonstrated a high H₂O₂ production rate of 27.22 mmol g⁻¹ h⁻¹ in pure water.
• Achieved highly selective 2e⁻ ORR due to synchronized proton and electron transfer.
• Exhibited significant proton conductivity (6.09 × 10⁻⁵ S cm⁻¹) and an extended excited-state lifetime (94.45 ps).

Conclusions:

• The developed D-A COF enables efficient and selective photocatalytic H₂O₂ synthesis via DCPET.
• The material's design overcomes kinetic limitations in heterogeneous photocatalysis.
• This work presents a new paradigm for designing advanced photocatalysts based on concerted proton-electron transfer mechanisms.